Add object type checks on the inputs of all functions

19 files changed, 271 insertions, 7 deletions

diff --git a/libappstream-glib/as-agreement-section.c b/libappstream-glib/as-agreement-section.c
index aa29098..42ece60 100644
--- a/libappstream-glib/as-agreement-section.c
+++ b/libappstream-glib/as-agreement-section.c
@@ -90,6 +90,7 @@ const gchar *
 as_agreement_section_get_kind (AsAgreementSection *agreement_section)
 {
 	AsAgreementSectionPrivate *priv = GET_PRIVATE (agreement_section);
+	g_return_val_if_fail (AS_IS_AGREEMENT_SECTION (agreement_section), NULL);
 	return priv->kind;
 }
 
@@ -106,6 +107,7 @@ void
 as_agreement_section_set_kind (AsAgreementSection *agreement_section, const gchar *kind)
 {
 	AsAgreementSectionPrivate *priv = GET_PRIVATE (agreement_section);
+	g_return_if_fail (AS_IS_AGREEMENT_SECTION (agreement_section));
 	as_ref_string_assign_safe (&priv->kind, kind);
 }
 
@@ -124,6 +126,7 @@ const gchar *
 as_agreement_section_get_name (AsAgreementSection *agreement_section, const gchar *locale)
 {
 	AsAgreementSectionPrivate *priv = GET_PRIVATE (agreement_section);
+	g_return_val_if_fail (AS_IS_AGREEMENT_SECTION (agreement_section), NULL);
 	return priv->name;
 }
 
@@ -142,6 +145,7 @@ as_agreement_section_set_name (AsAgreementSection *agreement_section,
 			       const gchar *locale, const gchar *name)
 {
 	AsAgreementSectionPrivate *priv = GET_PRIVATE (agreement_section);
+	g_return_if_fail (AS_IS_AGREEMENT_SECTION (agreement_section));
 	as_ref_string_assign_safe (&priv->name, name);
 }
 
@@ -161,6 +165,7 @@ as_agreement_section_get_description (AsAgreementSection *agreement_section,
 				      const gchar *locale)
 {
 	AsAgreementSectionPrivate *priv = GET_PRIVATE (agreement_section);
+	g_return_val_if_fail (AS_IS_AGREEMENT_SECTION (agreement_section), NULL);
 	return priv->desc;
 }
 
@@ -179,6 +184,7 @@ as_agreement_section_set_description (AsAgreementSection *agreement_section,
 				      const gchar *locale, const gchar *desc)
 {
 	AsAgreementSectionPrivate *priv = GET_PRIVATE (agreement_section);
+	g_return_if_fail (AS_IS_AGREEMENT_SECTION (agreement_section));
 	as_ref_string_assign_safe (&priv->desc, desc);
 }
 
@@ -200,6 +206,7 @@ as_agreement_section_node_insert (AsAgreementSection *agreement_section,
 				  AsNodeContext *ctx)
 {
 	AsAgreementSectionPrivate *priv = GET_PRIVATE (agreement_section);
+	g_return_val_if_fail (AS_IS_AGREEMENT_SECTION (agreement_section), NULL);
 	GNode *n = as_node_insert (parent, "agreement_section", NULL,
 				   AS_NODE_INSERT_FLAG_NONE,
 				   NULL);
diff --git a/libappstream-glib/as-agreement.c b/libappstream-glib/as-agreement.c
index 8c78204..c73347b 100644
--- a/libappstream-glib/as-agreement.c
+++ b/libappstream-glib/as-agreement.c
@@ -133,6 +133,7 @@ AsAgreementKind
 as_agreement_get_kind (AsAgreement *agreement)
 {
 	AsAgreementPrivate *priv = GET_PRIVATE (agreement);
+	g_return_val_if_fail (AS_IS_AGREEMENT (agreement), AS_AGREEMENT_KIND_UNKNOWN);
 	return priv->kind;
 }
 
@@ -149,6 +150,7 @@ void
 as_agreement_set_kind (AsAgreement *agreement, AsAgreementKind kind)
 {
 	AsAgreementPrivate *priv = GET_PRIVATE (agreement);
+	g_return_if_fail (AS_IS_AGREEMENT (agreement));
 	priv->kind = kind;
 }
 
@@ -166,6 +168,7 @@ const gchar *
 as_agreement_get_version_id (AsAgreement *agreement)
 {
 	AsAgreementPrivate *priv = GET_PRIVATE (agreement);
+	g_return_val_if_fail (AS_IS_AGREEMENT (agreement), NULL);
 	return priv->version_id;
 }
 
@@ -182,6 +185,7 @@ void
 as_agreement_set_version_id (AsAgreement *agreement, const gchar *version_id)
 {
 	AsAgreementPrivate *priv = GET_PRIVATE (agreement);
+	g_return_if_fail (AS_IS_AGREEMENT (agreement));
 	as_ref_string_assign_safe (&priv->version_id, version_id);
 }
 
@@ -199,6 +203,7 @@ GPtrArray *
 as_agreement_get_sections (AsAgreement *agreement)
 {
 	AsAgreementPrivate *priv = GET_PRIVATE (agreement);
+	g_return_val_if_fail (AS_IS_AGREEMENT (agreement), NULL);
 	return priv->sections;
 }
 
@@ -216,6 +221,7 @@ AsAgreementSection *
 as_agreement_get_section_default (AsAgreement *agreement)
 {
 	AsAgreementPrivate *priv = GET_PRIVATE (agreement);
+	g_return_val_if_fail (AS_IS_AGREEMENT (agreement), NULL);
 	if (priv->sections->len == 0)
 		return NULL;
 	return AS_AGREEMENT_SECTION (g_ptr_array_index (priv->sections, 0));
@@ -234,6 +240,7 @@ void
 as_agreement_add_section (AsAgreement *agreement, AsAgreementSection *agreement_section)
 {
 	AsAgreementPrivate *priv = GET_PRIVATE (agreement);
+	g_return_if_fail (AS_IS_AGREEMENT (agreement));
 	g_ptr_array_add (priv->sections, g_object_ref (agreement_section));
 }
 
@@ -255,6 +262,7 @@ as_agreement_node_insert (AsAgreement *agreement,
 			       AsNodeContext *ctx)
 {
 	AsAgreementPrivate *priv = GET_PRIVATE (agreement);
+	g_return_val_if_fail (AS_IS_AGREEMENT (agreement), NULL);
 	GNode *n = as_node_insert (parent, "agreement", NULL,
 				   AS_NODE_INSERT_FLAG_NONE,
 				   NULL);
diff --git a/libappstream-glib/as-bundle.c b/libappstream-glib/as-bundle.c
index e5afa9e..c8a8d7e 100644
--- a/libappstream-glib/as-bundle.c
+++ b/libappstream-glib/as-bundle.c
@@ -153,6 +153,7 @@ const gchar *
 as_bundle_get_id (AsBundle *bundle)
 {
 	AsBundlePrivate *priv = GET_PRIVATE (bundle);
+	g_return_val_if_fail (AS_IS_BUNDLE (bundle), NULL);
 	return priv->id;
 }
 
@@ -170,6 +171,7 @@ const gchar *
 as_bundle_get_runtime (AsBundle *bundle)
 {
 	AsBundlePrivate *priv = GET_PRIVATE (bundle);
+	g_return_val_if_fail (AS_IS_BUNDLE (bundle), NULL);
 	return priv->runtime;
 }
 
@@ -187,6 +189,7 @@ const gchar *
 as_bundle_get_sdk (AsBundle *bundle)
 {
 	AsBundlePrivate *priv = GET_PRIVATE (bundle);
+	g_return_val_if_fail (AS_IS_BUNDLE (bundle), NULL);
 	return priv->sdk;
 }
 
@@ -204,6 +207,7 @@ AsBundleKind
 as_bundle_get_kind (AsBundle *bundle)
 {
 	AsBundlePrivate *priv = GET_PRIVATE (bundle);
+	g_return_val_if_fail (AS_IS_BUNDLE (bundle), AS_BUNDLE_KIND_UNKNOWN);
 	return priv->kind;
 }
 
@@ -220,6 +224,7 @@ void
 as_bundle_set_id (AsBundle *bundle, const gchar *id)
 {
 	AsBundlePrivate *priv = GET_PRIVATE (bundle);
+	g_return_if_fail (AS_IS_BUNDLE (bundle));
 	as_ref_string_assign_safe (&priv->id, id);
 }
 
@@ -236,6 +241,7 @@ void
 as_bundle_set_runtime (AsBundle *bundle, const gchar *runtime)
 {
 	AsBundlePrivate *priv = GET_PRIVATE (bundle);
+	g_return_if_fail (AS_IS_BUNDLE (bundle));
 	as_ref_string_assign_safe (&priv->runtime, runtime);
 }
 
@@ -252,6 +258,7 @@ void
 as_bundle_set_sdk (AsBundle *bundle, const gchar *sdk)
 {
 	AsBundlePrivate *priv = GET_PRIVATE (bundle);
+	g_return_if_fail (AS_IS_BUNDLE (bundle));
 	as_ref_string_assign_safe (&priv->sdk, sdk);
 }
 
@@ -268,6 +275,7 @@ void
 as_bundle_set_kind (AsBundle *bundle, AsBundleKind kind)
 {
 	AsBundlePrivate *priv = GET_PRIVATE (bundle);
+	g_return_if_fail (AS_IS_BUNDLE (bundle));
 	priv->kind = kind;
 }
 
@@ -289,6 +297,8 @@ as_bundle_node_insert (AsBundle *bundle, GNode *parent, AsNodeContext *ctx)
 	AsBundlePrivate *priv = GET_PRIVATE (bundle);
 	GNode *n;
 
+	g_return_val_if_fail (AS_IS_BUNDLE (bundle), NULL);
+
 	n = as_node_insert (parent, "bundle", priv->id,
 			    AS_NODE_INSERT_FLAG_NONE,
 			    "type", as_bundle_kind_to_string (priv->kind),
@@ -321,6 +331,8 @@ as_bundle_node_parse (AsBundle *bundle, GNode *node,
 	AsBundlePrivate *priv = GET_PRIVATE (bundle);
 	const gchar *tmp;
 
+	g_return_val_if_fail (AS_IS_BUNDLE (bundle), FALSE);
+
 	tmp = as_node_get_attribute (node, "type");
 	as_bundle_set_kind (bundle, as_bundle_kind_from_string (tmp));
 
diff --git a/libappstream-glib/as-checksum.c b/libappstream-glib/as-checksum.c
index 7117d4a..832b0df 100644
--- a/libappstream-glib/as-checksum.c
+++ b/libappstream-glib/as-checksum.c
@@ -138,6 +138,7 @@ const gchar *
 as_checksum_get_filename (AsChecksum *checksum)
 {
 	AsChecksumPrivate *priv = GET_PRIVATE (checksum);
+	g_return_val_if_fail (AS_IS_CHECKSUM (checksum), NULL);
 	return priv->filename;
 }
 
@@ -155,6 +156,7 @@ const gchar *
 as_checksum_get_value (AsChecksum *checksum)
 {
 	AsChecksumPrivate *priv = GET_PRIVATE (checksum);
+	g_return_val_if_fail (AS_IS_CHECKSUM (checksum), NULL);
 	return priv->value;
 }
 
@@ -172,6 +174,7 @@ GChecksumType
 as_checksum_get_kind (AsChecksum *checksum)
 {
 	AsChecksumPrivate *priv = GET_PRIVATE (checksum);
+	g_return_val_if_fail (AS_IS_CHECKSUM (checksum), AS_CHECKSUM_UNKNOWN);
 	return priv->kind;
 }
 
@@ -189,6 +192,7 @@ AsChecksumTarget
 as_checksum_get_target (AsChecksum *checksum)
 {
 	AsChecksumPrivate *priv = GET_PRIVATE (checksum);
+	g_return_val_if_fail (AS_IS_CHECKSUM (checksum), AS_CHECKSUM_TARGET_UNKNOWN);
 	return priv->target;
 }
 
@@ -206,6 +210,7 @@ as_checksum_set_filename (AsChecksum *checksum,
 			  const gchar *filename)
 {
 	AsChecksumPrivate *priv = GET_PRIVATE (checksum);
+	g_return_if_fail (AS_IS_CHECKSUM (checksum));
 	as_ref_string_assign_safe (&priv->filename, filename);
 }
 
@@ -222,6 +227,7 @@ void
 as_checksum_set_value (AsChecksum *checksum, const gchar *value)
 {
 	AsChecksumPrivate *priv = GET_PRIVATE (checksum);
+	g_return_if_fail (AS_IS_CHECKSUM (checksum));
 	as_ref_string_assign_safe (&priv->value, value);
 }
 
@@ -238,6 +244,7 @@ void
 as_checksum_set_kind (AsChecksum *checksum, GChecksumType kind)
 {
 	AsChecksumPrivate *priv = GET_PRIVATE (checksum);
+	g_return_if_fail (AS_IS_CHECKSUM (checksum));
 	priv->kind = kind;
 }
 
@@ -254,6 +261,7 @@ void
 as_checksum_set_target (AsChecksum *checksum, AsChecksumTarget target)
 {
 	AsChecksumPrivate *priv = GET_PRIVATE (checksum);
+	g_return_if_fail (AS_IS_CHECKSUM (checksum));
 	priv->target = target;
 }
 
@@ -303,6 +311,8 @@ as_checksum_node_insert (AsChecksum *checksum, GNode *parent, AsNodeContext *ctx
 	AsChecksumPrivate *priv = GET_PRIVATE (checksum);
 	GNode *n;
 
+	g_return_val_if_fail (AS_IS_CHECKSUM (checksum), NULL);
+
 	n = as_node_insert (parent, "checksum", priv->value,
 			    AS_NODE_INSERT_FLAG_NONE,
 			    NULL);
@@ -339,6 +349,8 @@ as_checksum_node_parse (AsChecksum *checksum, GNode *node,
 	AsChecksumPrivate *priv = GET_PRIVATE (checksum);
 	const gchar *tmp;
 
+	g_return_val_if_fail (AS_IS_CHECKSUM (checksum), FALSE);
+
 	tmp = as_node_get_attribute (node, "type");
 	if (tmp != NULL)
 		priv->kind = _g_checksum_type_from_string (tmp);
diff --git a/libappstream-glib/as-content-rating.c b/libappstream-glib/as-content-rating.c
index bab06bb..eb3afae 100644
--- a/libappstream-glib/as-content-rating.c
+++ b/libappstream-glib/as-content-rating.c
@@ -102,6 +102,7 @@ AsContentRatingValue
 as_content_rating_get_value (AsContentRating *content_rating, const gchar *id)
 {
 	AsContentRatingPrivate *priv = GET_PRIVATE (content_rating);
+	g_return_val_if_fail (AS_IS_CONTENT_RATING (content_rating), AS_CONTENT_RATING_VALUE_UNKNOWN);
 	guint i;
 	for (i = 0; i < priv->keys->len; i++) {
 		AsContentRatingKey *key = g_ptr_array_index (priv->keys, i);
@@ -314,6 +315,8 @@ as_content_rating_get_minimum_age (AsContentRating *content_rating)
 	guint i;
 	guint csm_age = 0;
 
+	g_return_val_if_fail (AS_IS_CONTENT_RATING (content_rating), 0);
+
 	/* check kind */
 	if (g_strcmp0 (priv->kind, "oars-1.0") != 0 &&
 	    g_strcmp0 (priv->kind, "oars-1.1") != 0)
@@ -344,6 +347,7 @@ const gchar *
 as_content_rating_get_kind (AsContentRating *content_rating)
 {
 	AsContentRatingPrivate *priv = GET_PRIVATE (content_rating);
+	g_return_val_if_fail (AS_IS_CONTENT_RATING (content_rating), NULL);
 	return priv->kind;
 }
 
@@ -360,6 +364,7 @@ void
 as_content_rating_set_kind (AsContentRating *content_rating, const gchar *kind)
 {
 	AsContentRatingPrivate *priv = GET_PRIVATE (content_rating);
+	g_return_if_fail (AS_IS_CONTENT_RATING (content_rating));
 	as_ref_string_assign_safe (&priv->kind, kind);
 }
 
@@ -385,6 +390,8 @@ as_content_rating_node_insert (AsContentRating *content_rating,
 	GNode *n;
 	guint i;
 
+	g_return_val_if_fail (AS_IS_CONTENT_RATING (content_rating), NULL);
+
 	n = as_node_insert (parent, "content_rating", NULL,
 			    AS_NODE_INSERT_FLAG_NONE,
 			    NULL);
@@ -424,6 +431,8 @@ as_content_rating_node_parse (AsContentRating *content_rating, GNode *node,
 	const gchar *tmp;
 	g_autoptr(GHashTable) captions = NULL;
 
+	g_return_val_if_fail (AS_IS_CONTENT_RATING (content_rating), FALSE);
+
 	/* get ID */
 	tmp = as_node_get_attribute (node, "type");
 	if (tmp != NULL)
diff --git a/libappstream-glib/as-format.c b/libappstream-glib/as-format.c
index 0ef29c9..96919e6 100644
--- a/libappstream-glib/as-format.c
+++ b/libappstream-glib/as-format.c
@@ -132,6 +132,7 @@ const gchar *
 as_format_get_filename (AsFormat *format)
 {
 	AsFormatPrivate *priv = GET_PRIVATE (format);
+	g_return_val_if_fail (AS_IS_FORMAT (format), NULL);
 	return priv->filename;
 }
 
@@ -149,6 +150,7 @@ AsFormatKind
 as_format_get_kind (AsFormat *format)
 {
 	AsFormatPrivate *priv = GET_PRIVATE (format);
+	g_return_val_if_fail (AS_IS_FORMAT (format), AS_FORMAT_KIND_UNKNOWN);
 	return priv->kind;
 }
 
@@ -201,6 +203,7 @@ void
 as_format_set_filename (AsFormat *format, const gchar *filename)
 {
 	AsFormatPrivate *priv = GET_PRIVATE (format);
+	g_return_if_fail (AS_IS_FORMAT (format));
 	if (priv->kind == AS_FORMAT_KIND_UNKNOWN)
 		priv->kind = as_format_guess_kind (filename);
 	as_ref_string_assign_safe (&priv->filename, filename);
@@ -219,6 +222,7 @@ void
 as_format_set_kind (AsFormat *format, AsFormatKind kind)
 {
 	AsFormatPrivate *priv = GET_PRIVATE (format);
+	g_return_if_fail (AS_IS_FORMAT (format));
 	priv->kind = kind;
 }
 
@@ -239,6 +243,9 @@ as_format_equal (AsFormat *format1, AsFormat *format2)
 	AsFormatPrivate *priv1 = GET_PRIVATE (format1);
 	AsFormatPrivate *priv2 = GET_PRIVATE (format2);
 
+	g_return_val_if_fail (AS_IS_FORMAT (format1), FALSE);
+	g_return_val_if_fail (AS_IS_FORMAT (format2), FALSE);
+
 	/* trivial */
 	if (format1 == format2)
 		return TRUE;
diff --git a/libappstream-glib/as-icon.c b/libappstream-glib/as-icon.c
index 9f5a0dc..01324a7 100644
--- a/libappstream-glib/as-icon.c
+++ b/libappstream-glib/as-icon.c
@@ -172,6 +172,7 @@ const gchar *
 as_icon_get_name (AsIcon *icon)
 {
 	AsIconPrivate *priv = GET_PRIVATE (icon);
+	g_return_val_if_fail (AS_IS_ICON (icon), NULL);
 	return priv->name;
 }
 
@@ -190,6 +191,7 @@ const gchar *
 as_icon_get_url (AsIcon *icon)
 {
 	AsIconPrivate *priv = GET_PRIVATE (icon);
+	g_return_val_if_fail (AS_IS_ICON (icon), NULL);
 	return priv->url;
 }
 
@@ -208,6 +210,7 @@ const gchar *
 as_icon_get_filename (AsIcon *icon)
 {
 	AsIconPrivate *priv = GET_PRIVATE (icon);
+	g_return_val_if_fail (AS_IS_ICON (icon), NULL);
 	return priv->filename;
 }
 
@@ -226,6 +229,8 @@ as_icon_get_prefix (AsIcon *icon)
 {
 	AsIconPrivate *priv = GET_PRIVATE (icon);
 
+	g_return_val_if_fail (AS_IS_ICON (icon), NULL);
+
 	/* only use the size if the metadata has width and height */
 	if (priv->prepend_size && priv->prefix_private == NULL) {
 		g_autofree gchar *sz = NULL;
@@ -263,6 +268,7 @@ guint
 as_icon_get_width (AsIcon *icon)
 {
 	AsIconPrivate *priv = GET_PRIVATE (icon);
+	g_return_val_if_fail (AS_IS_ICON (icon), 0);
 	return priv->width;
 }
 
@@ -280,6 +286,7 @@ guint
 as_icon_get_height (AsIcon *icon)
 {
 	AsIconPrivate *priv = GET_PRIVATE (icon);
+	g_return_val_if_fail (AS_IS_ICON (icon), 0);
 	return priv->height;
 }
 
@@ -297,6 +304,7 @@ guint
 as_icon_get_scale (AsIcon *icon)
 {
 	AsIconPrivate *priv = GET_PRIVATE (icon);
+	g_return_val_if_fail (AS_IS_ICON (icon), 0);
 	return priv->scale;
 }
 
@@ -314,6 +322,7 @@ AsIconKind
 as_icon_get_kind (AsIcon *icon)
 {
 	AsIconPrivate *priv = GET_PRIVATE (icon);
+	g_return_val_if_fail (AS_IS_ICON (icon), AS_ICON_KIND_UNKNOWN);
 	return priv->kind;
 }
 
@@ -331,6 +340,7 @@ GdkPixbuf *
 as_icon_get_pixbuf (AsIcon *icon)
 {
 	AsIconPrivate *priv = GET_PRIVATE (icon);
+	g_return_val_if_fail (AS_IS_ICON (icon), NULL);
 	return priv->pixbuf;
 }
 
@@ -348,6 +358,7 @@ GBytes *
 as_icon_get_data (AsIcon *icon)
 {
 	AsIconPrivate *priv = GET_PRIVATE (icon);
+	g_return_val_if_fail (AS_IS_ICON (icon), NULL);
 	return priv->data;
 }
 
@@ -364,6 +375,7 @@ void
 as_icon_set_name (AsIcon *icon, const gchar *name)
 {
 	AsIconPrivate *priv = GET_PRIVATE (icon);
+	g_return_if_fail (AS_IS_ICON (icon));
 	as_ref_string_assign_safe (&priv->name, name);
 }
 
@@ -380,6 +392,7 @@ void
 as_icon_set_prefix (AsIcon *icon, const gchar *prefix)
 {
 	AsIconPrivate *priv = GET_PRIVATE (icon);
+	g_return_if_fail (AS_IS_ICON (icon));
 	as_ref_string_assign_safe (&priv->prefix, prefix);
 }
 
@@ -387,6 +400,7 @@ void
 as_icon_set_prefix_rstr (AsIcon *icon, AsRefString *rstr)
 {
 	AsIconPrivate *priv = GET_PRIVATE (icon);
+	g_return_if_fail (AS_IS_ICON (icon));
 	as_ref_string_assign (&priv->prefix, rstr);
 }
 
@@ -403,6 +417,7 @@ void
 as_icon_set_url (AsIcon *icon, const gchar *url)
 {
 	AsIconPrivate *priv = GET_PRIVATE (icon);
+	g_return_if_fail (AS_IS_ICON (icon));
 	as_ref_string_assign_safe (&priv->url, url);
 }
 
@@ -419,6 +434,7 @@ void
 as_icon_set_filename (AsIcon *icon, const gchar *filename)
 {
 	AsIconPrivate *priv = GET_PRIVATE (icon);
+	g_return_if_fail (AS_IS_ICON (icon));
 	as_ref_string_assign_safe (&priv->filename, filename);
 }
 
@@ -435,6 +451,7 @@ void
 as_icon_set_width (AsIcon *icon, guint width)
 {
 	AsIconPrivate *priv = GET_PRIVATE (icon);
+	g_return_if_fail (AS_IS_ICON (icon));
 	priv->width = width;
 }
 
@@ -451,6 +468,7 @@ void
 as_icon_set_height (AsIcon *icon, guint height)
 {
 	AsIconPrivate *priv = GET_PRIVATE (icon);
+	g_return_if_fail (AS_IS_ICON (icon));
 	priv->height = height;
 }
 
@@ -467,6 +485,7 @@ void
 as_icon_set_scale (AsIcon *icon, guint scale)
 {
 	AsIconPrivate *priv = GET_PRIVATE (icon);
+	g_return_if_fail (AS_IS_ICON (icon));
 	priv->scale = scale;
 }
 
@@ -483,6 +502,7 @@ void
 as_icon_set_kind (AsIcon *icon, AsIconKind kind)
 {
 	AsIconPrivate *priv = GET_PRIVATE (icon);
+	g_return_if_fail (AS_IS_ICON (icon));
 	priv->kind = kind;
 }
 
@@ -499,6 +519,7 @@ void
 as_icon_set_pixbuf (AsIcon *icon, GdkPixbuf *pixbuf)
 {
 	AsIconPrivate *priv = GET_PRIVATE (icon);
+	g_return_if_fail (AS_IS_ICON (icon));
 	g_set_object (&priv->pixbuf, pixbuf);
 	if (pixbuf != NULL) {
 		priv->width = (guint) gdk_pixbuf_get_width (pixbuf);
@@ -520,6 +541,8 @@ as_icon_set_data (AsIcon *icon, GBytes *data)
 {
 	AsIconPrivate *priv = GET_PRIVATE (icon);
 
+	g_return_if_fail (AS_IS_ICON (icon));
+
 	if (priv->data != NULL)
 		g_bytes_unref (priv->data);
 	if (data == NULL) {
@@ -570,6 +593,8 @@ as_icon_node_insert (AsIcon *icon, GNode *parent, AsNodeContext *ctx)
 	AsIconPrivate *priv = GET_PRIVATE (icon);
 	GNode *n;
 
+	g_return_val_if_fail (AS_IS_ICON (icon), NULL);
+
 	/* embedded icon */
 	if (priv->kind == AS_ICON_KIND_EMBEDDED)
 		return as_icon_node_insert_embedded (icon, parent, ctx);
@@ -686,6 +711,8 @@ as_icon_node_parse (AsIcon *icon, GNode *node,
 	AsRefString *str;
 	guint size;
 
+	g_return_val_if_fail (AS_IS_ICON (icon), FALSE);
+
 	str = as_node_get_attribute_as_refstr (node, "type");
 	as_icon_set_kind (icon, as_icon_kind_from_string (str));
 	switch (priv->kind) {
@@ -767,6 +794,8 @@ as_icon_node_parse_dep11 (AsIcon *icon, GNode *node,
 	GNode *n;
 	AsIconPrivate *priv = GET_PRIVATE (icon);
 
+	g_return_val_if_fail (AS_IS_ICON (icon), FALSE);
+
 	for (n = node->children; n != NULL; n = n->next) {
 		const gchar *key;
 		guint size;
@@ -840,6 +869,8 @@ as_icon_load (AsIcon *icon, AsIconLoadFlags flags, GError **error)
 	g_autofree gchar *fn_fallback = NULL;
 	g_autoptr(GdkPixbuf) pixbuf = NULL;
 
+	g_return_val_if_fail (AS_IS_ICON (icon), FALSE);
+
 	/* absolute filename */
 	if (priv->kind == AS_ICON_KIND_LOCAL) {
 		if (priv->filename == NULL) {
@@ -916,6 +947,8 @@ as_icon_convert_to_kind (AsIcon *icon, AsIconKind kind, GError **error)
 {
 	AsIconPrivate *priv = GET_PRIVATE (icon);
 
+	g_return_val_if_fail (AS_IS_ICON (icon), FALSE);
+
 	/* these can't be converted */
 	if (priv->kind == AS_ICON_KIND_STOCK ||
 	    priv->kind == AS_ICON_KIND_REMOTE)
diff --git a/libappstream-glib/as-image.c b/libappstream-glib/as-image.c
index 5b6f1f9..e5b00d2 100644
--- a/libappstream-glib/as-image.c
+++ b/libappstream-glib/as-image.c
@@ -143,6 +143,7 @@ const gchar *
 as_image_get_url (AsImage *image)
 {
 	AsImagePrivate *priv = GET_PRIVATE (image);
+	g_return_val_if_fail (AS_IS_IMAGE (image), NULL);
 	return priv->url;
 }
 
@@ -160,6 +161,7 @@ const gchar *
 as_image_get_basename (AsImage *image)
 {
 	AsImagePrivate *priv = GET_PRIVATE (image);
+	g_return_val_if_fail (AS_IS_IMAGE (image), NULL);
 	return priv->basename;
 }
 
@@ -177,6 +179,7 @@ const gchar *
 as_image_get_locale (AsImage *image)
 {
 	AsImagePrivate *priv = GET_PRIVATE (image);
+	g_return_val_if_fail (AS_IS_IMAGE (image), NULL);
 	return priv->locale;
 }
 
@@ -194,6 +197,7 @@ const gchar *
 as_image_get_md5 (AsImage *image)
 {
 	AsImagePrivate *priv = GET_PRIVATE (image);
+	g_return_val_if_fail (AS_IS_IMAGE (image), NULL);
 	return priv->md5;
 }
 
@@ -211,6 +215,7 @@ guint
 as_image_get_width (AsImage *image)
 {
 	AsImagePrivate *priv = GET_PRIVATE (image);
+	g_return_val_if_fail (AS_IS_IMAGE (image), 0);
 	return priv->width;
 }
 
@@ -228,6 +233,7 @@ guint
 as_image_get_height (AsImage *image)
 {
 	AsImagePrivate *priv = GET_PRIVATE (image);
+	g_return_val_if_fail (AS_IS_IMAGE (image), 0);
 	return priv->height;
 }
 
@@ -245,6 +251,7 @@ AsImageKind
 as_image_get_kind (AsImage *image)
 {
 	AsImagePrivate *priv = GET_PRIVATE (image);
+	g_return_val_if_fail (AS_IS_IMAGE (image), AS_IMAGE_KIND_UNKNOWN);
 	return priv->kind;
 }
 
@@ -262,6 +269,7 @@ GdkPixbuf *
 as_image_get_pixbuf (AsImage *image)
 {
 	AsImagePrivate *priv = GET_PRIVATE (image);
+	g_return_val_if_fail (AS_IS_IMAGE (image), NULL);
 	return priv->pixbuf;
 }
 
@@ -278,6 +286,7 @@ void
 as_image_set_url (AsImage *image, const gchar *url)
 {
 	AsImagePrivate *priv = GET_PRIVATE (image);
+	g_return_if_fail (AS_IS_IMAGE (image));
 	as_ref_string_assign_safe (&priv->url, url);
 }
 
@@ -285,6 +294,7 @@ void
 as_image_set_url_rstr (AsImage *image, AsRefString *rstr)
 {
 	AsImagePrivate *priv = GET_PRIVATE (image);
+	g_return_if_fail (AS_IS_IMAGE (image));
 	as_ref_string_assign (&priv->url, rstr);
 }
 
@@ -301,6 +311,7 @@ void
 as_image_set_basename (AsImage *image, const gchar *basename)
 {
 	AsImagePrivate *priv = GET_PRIVATE (image);
+	g_return_if_fail (AS_IS_IMAGE (image));
 	as_ref_string_assign_safe (&priv->basename, basename);
 }
 
@@ -317,6 +328,7 @@ void
 as_image_set_locale (AsImage *image, const gchar *locale)
 {
 	AsImagePrivate *priv = GET_PRIVATE (image);
+	g_return_if_fail (AS_IS_IMAGE (image));
 	as_ref_string_assign_safe (&priv->locale, locale);
 }
 
@@ -333,6 +345,7 @@ void
 as_image_set_width (AsImage *image, guint width)
 {
 	AsImagePrivate *priv = GET_PRIVATE (image);
+	g_return_if_fail (AS_IS_IMAGE (image));
 	priv->width = width;
 }
 
@@ -349,6 +362,7 @@ void
 as_image_set_height (AsImage *image, guint height)
 {
 	AsImagePrivate *priv = GET_PRIVATE (image);
+	g_return_if_fail (AS_IS_IMAGE (image));
 	priv->height = height;
 }
 
@@ -365,6 +379,7 @@ void
 as_image_set_kind (AsImage *image, AsImageKind kind)
 {
 	AsImagePrivate *priv = GET_PRIVATE (image);
+	g_return_if_fail (AS_IS_IMAGE (image));
 	priv->kind = kind;
 }
 
@@ -384,6 +399,8 @@ as_image_set_pixbuf (AsImage *image, GdkPixbuf *pixbuf)
 	guchar *data;
 	guint len;
 
+	g_return_if_fail (AS_IS_IMAGE (image));
+
 	g_set_object (&priv->pixbuf, pixbuf);
 	if (pixbuf == NULL)
 		return;
@@ -415,6 +432,7 @@ as_image_node_insert (AsImage *image, GNode *parent, AsNodeContext *ctx)
 {
 	AsImagePrivate *priv = GET_PRIVATE (image);
 	GNode *n;
+	g_return_val_if_fail (AS_IS_IMAGE (image), NULL);
 	n = as_node_insert (parent, "image", priv->url,
 			    AS_NODE_INSERT_FLAG_NONE,
 			    NULL);
@@ -450,6 +468,8 @@ as_image_node_parse (AsImage *image, GNode *node,
 	const gchar *tmp;
 	guint size;
 
+	g_return_val_if_fail (AS_IS_IMAGE (image), FALSE);
+
 	size = as_node_get_attribute_as_uint (node, "width");
 	if (size != G_MAXUINT)
 		as_image_set_width (image, size);
@@ -538,6 +558,8 @@ as_image_load_filename_full (AsImage *image,
 	g_autoptr(GdkPixbuf) pixbuf_src = NULL;
 	g_autoptr(GdkPixbuf) pixbuf_tmp = NULL;
 
+	g_return_val_if_fail (AS_IS_IMAGE (image), FALSE);
+
 	/* only support non-deprecated types */
 	if (flags & AS_IMAGE_LOAD_FLAG_ONLY_SUPPORTED) {
 		GdkPixbufFormat *fmt;
@@ -749,6 +771,8 @@ as_image_save_pixbuf (AsImage *image,
 	guint pixbuf_width;
 	g_autoptr(GdkPixbuf) pixbuf_tmp = NULL;
 
+	g_return_val_if_fail (AS_IS_IMAGE (image), NULL);
+
 	/* never set */
 	if (priv->pixbuf == NULL)
 		return NULL;
@@ -900,6 +924,8 @@ as_image_get_alpha_flags (AsImage *image)
 	guint cnt_content_to_alpha_h;
 	guint cnt_content_to_alpha_v = 0;
 
+	g_return_val_if_fail (AS_IS_IMAGE (image), AS_IMAGE_ALPHA_FLAG_NONE);
+
 	if (!gdk_pixbuf_get_has_alpha (priv->pixbuf))
 		return AS_IMAGE_ALPHA_FLAG_NONE;
 
@@ -1006,6 +1032,9 @@ as_image_equal (AsImage *image1, AsImage *image2)
 	AsImagePrivate *priv1 = GET_PRIVATE (image1);
 	AsImagePrivate *priv2 = GET_PRIVATE (image2);
 
+	g_return_val_if_fail (AS_IS_IMAGE (image1), FALSE);
+	g_return_val_if_fail (AS_IS_IMAGE (image2), FALSE);
+
 	/* trivial */
 	if (image1 == image2)
 		return TRUE;
diff --git a/libappstream-glib/as-launchable.c b/libappstream-glib/as-launchable.c
index 51704f7..151d641 100644
--- a/libappstream-glib/as-launchable.c
+++ b/libappstream-glib/as-launchable.c
@@ -137,6 +137,7 @@ const gchar *
 as_launchable_get_value (AsLaunchable *launchable)
 {
 	AsLaunchablePrivate *priv = GET_PRIVATE (launchable);
+	g_return_val_if_fail (AS_IS_LAUNCHABLE (launchable), NULL);
 	return priv->value;
 }
 
@@ -154,6 +155,7 @@ AsLaunchableKind
 as_launchable_get_kind (AsLaunchable *launchable)
 {
 	AsLaunchablePrivate *priv = GET_PRIVATE (launchable);
+	g_return_val_if_fail (AS_IS_LAUNCHABLE (launchable), AS_LAUNCHABLE_KIND_UNKNOWN);
 	return priv->kind;
 }
 
@@ -170,6 +172,7 @@ void
 as_launchable_set_value (AsLaunchable *launchable, const gchar *value)
 {
 	AsLaunchablePrivate *priv = GET_PRIVATE (launchable);
+	g_return_if_fail (AS_IS_LAUNCHABLE (launchable));
 	as_ref_string_assign_safe (&priv->value, value);
 }
 
@@ -186,6 +189,7 @@ void
 as_launchable_set_kind (AsLaunchable *launchable, AsLaunchableKind kind)
 {
 	AsLaunchablePrivate *priv = GET_PRIVATE (launchable);
+	g_return_if_fail (AS_IS_LAUNCHABLE (launchable));
 	priv->kind = kind;
 }
 
@@ -205,10 +209,12 @@ GNode *
 as_launchable_node_insert (AsLaunchable *launchable, GNode *parent, AsNodeContext *ctx)
 {
 	AsLaunchablePrivate *priv = GET_PRIVATE (launchable);
-	GNode *n = as_node_insert (parent, "launchable",
-				   priv->value,
-				   AS_NODE_INSERT_FLAG_NONE,
-				   NULL);
+	GNode *n;
+	g_return_val_if_fail (AS_IS_LAUNCHABLE (launchable), NULL);
+	n = as_node_insert (parent, "launchable",
+			    priv->value,
+			    AS_NODE_INSERT_FLAG_NONE,
+			    NULL);
 	if (priv->kind != AS_LAUNCHABLE_KIND_UNKNOWN)
 		as_node_add_attribute (n, "type", as_launchable_kind_to_string (priv->kind));
 	return n;
@@ -252,6 +258,7 @@ as_launchable_node_parse (AsLaunchable *launchable, GNode *node,
 			  AsNodeContext *ctx, GError **error)
 {
 	AsLaunchablePrivate *priv = GET_PRIVATE (launchable);
+	g_return_val_if_fail (AS_IS_LAUNCHABLE (launchable), FALSE);
 	priv->kind = as_launchable_kind_from_string (as_node_get_attribute (node, "type"));
 	as_ref_string_assign (&priv->value, as_node_get_data_as_refstr (node));
 	return TRUE;
diff --git a/libappstream-glib/as-monitor.c b/libappstream-glib/as-monitor.c
index b4c3681..f7bdfce 100644
--- a/libappstream-glib/as-monitor.c
+++ b/libappstream-glib/as-monitor.c
@@ -418,6 +418,8 @@ as_monitor_add_directory (AsMonitor *monitor,
 	g_autoptr(GFile) file = NULL;
 	g_autoptr(GDir) dir = NULL;
 
+	g_return_val_if_fail (AS_IS_MONITOR (monitor), FALSE);
+
 	/* find the files already in the directory */
 	if (g_file_test (filename, G_FILE_TEST_EXISTS)) {
 		dir = g_dir_open (filename, 0, error);
@@ -467,6 +469,8 @@ as_monitor_add_file (AsMonitor *monitor,
 	g_autoptr(GFile) file = NULL;
 	g_autoptr(GFileMonitor) mon = NULL;
 
+	g_return_val_if_fail (AS_IS_MONITOR (monitor), FALSE);
+
 	/* already watched */
 	if (_g_ptr_array_str_find (priv->files, filename) != NULL)
 		return TRUE;
diff --git a/libappstream-glib/as-problem.c b/libappstream-glib/as-problem.c
index 69fe25a..92cf913 100644
--- a/libappstream-glib/as-problem.c
+++ b/libappstream-glib/as-problem.c
@@ -129,6 +129,7 @@ AsProblemKind
 as_problem_get_kind (AsProblem *problem)
 {
 	AsProblemPrivate *priv = GET_PRIVATE (problem);
+	g_return_val_if_fail (AS_IS_PROBLEM (problem), AS_PROBLEM_KIND_UNKNOWN);
 	return priv->kind;
 }
 
@@ -146,6 +147,7 @@ guint
 as_problem_get_line_number (AsProblem *problem)
 {
 	AsProblemPrivate *priv = GET_PRIVATE (problem);
+	g_return_val_if_fail (AS_IS_PROBLEM (problem), 0);
 	return priv->line_number;
 }
 
@@ -163,6 +165,7 @@ const gchar *
 as_problem_get_message (AsProblem *problem)
 {
 	AsProblemPrivate *priv = GET_PRIVATE (problem);
+	g_return_val_if_fail (AS_IS_PROBLEM (problem), NULL);
 	return priv->message;
 }
 
@@ -179,6 +182,7 @@ void
 as_problem_set_kind (AsProblem *problem, AsProblemKind kind)
 {
 	AsProblemPrivate *priv = GET_PRIVATE (problem);
+	g_return_if_fail (AS_IS_PROBLEM (problem));
 	priv->kind = kind;
 }
 
@@ -195,6 +199,7 @@ void
 as_problem_set_line_number (AsProblem *problem, guint line_number)
 {
 	AsProblemPrivate *priv = GET_PRIVATE (problem);
+	g_return_if_fail (AS_IS_PROBLEM (problem));
 	priv->line_number = line_number;
 }
 
@@ -211,6 +216,7 @@ void
 as_problem_set_message (AsProblem *problem, const gchar *message)
 {
 	AsProblemPrivate *priv = GET_PRIVATE (problem);
+	g_return_if_fail (AS_IS_PROBLEM (problem));
 	g_free (priv->message);
 	priv->message = g_strdup (message);
 }
diff --git a/libappstream-glib/as-provide.c b/libappstream-glib/as-provide.c
index b5ecde2..350bf35 100644
--- a/libappstream-glib/as-provide.c
+++ b/libappstream-glib/as-provide.c
@@ -164,6 +164,7 @@ const gchar *
 as_provide_get_value (AsProvide *provide)
 {
 	AsProvidePrivate *priv = GET_PRIVATE (provide);
+	g_return_val_if_fail (AS_IS_PROVIDE (provide), NULL);
 	return priv->value;
 }
 
@@ -181,6 +182,7 @@ AsProvideKind
 as_provide_get_kind (AsProvide *provide)
 {
 	AsProvidePrivate *priv = GET_PRIVATE (provide);
+	g_return_val_if_fail (AS_IS_PROVIDE (provide), AS_PROVIDE_KIND_UNKNOWN);
 	return priv->kind;
 }
 
@@ -197,6 +199,7 @@ void
 as_provide_set_value (AsProvide *provide, const gchar *value)
 {
 	AsProvidePrivate *priv = GET_PRIVATE (provide);
+	g_return_if_fail (AS_IS_PROVIDE (provide));
 	as_ref_string_assign_safe (&priv->value, value);
 }
 
@@ -213,6 +216,7 @@ void
 as_provide_set_kind (AsProvide *provide, AsProvideKind kind)
 {
 	AsProvidePrivate *priv = GET_PRIVATE (provide);
+	g_return_if_fail (AS_IS_PROVIDE (provide));
 	priv->kind = kind;
 }
 
@@ -234,6 +238,8 @@ as_provide_node_insert (AsProvide *provide, GNode *parent, AsNodeContext *ctx)
 	AsProvidePrivate *priv = GET_PRIVATE (provide);
 	GNode *n = NULL;
 
+	g_return_val_if_fail (AS_IS_PROVIDE (provide), NULL);
+
 	switch (priv->kind) {
 	case AS_PROVIDE_KIND_UNKNOWN:
 		break;
@@ -315,6 +321,8 @@ as_provide_node_parse (AsProvide *provide, GNode *node,
 	AsProvidePrivate *priv = GET_PRIVATE (provide);
 	const gchar *tmp;
 
+	g_return_val_if_fail (AS_IS_PROVIDE (provide), FALSE);
+
 	if (g_strcmp0 (as_node_get_name (node), "dbus") == 0) {
 		tmp = as_node_get_attribute (node, "type");
 		if (g_strcmp0 (tmp, "system") == 0)
diff --git a/libappstream-glib/as-release.c b/libappstream-glib/as-release.c
index 785bea4..034cbf6 100644
--- a/libappstream-glib/as-release.c
+++ b/libappstream-glib/as-release.c
@@ -238,6 +238,9 @@ as_release_vercmp (AsRelease *rel1, AsRelease *rel2)
 	AsReleasePrivate *priv2 = GET_PRIVATE (rel2);
 	gint val;
 
+	g_return_val_if_fail (AS_IS_RELEASE (rel1), 0);
+	g_return_val_if_fail (AS_IS_RELEASE (rel2), 0);
+
 	/* prefer the timestamp */
 	if (priv1->timestamp > priv2->timestamp)
 		return -1;
@@ -267,6 +270,7 @@ guint64
 as_release_get_size (AsRelease *release, AsSizeKind kind)
 {
 	AsReleasePrivate *priv = GET_PRIVATE (release);
+	g_return_val_if_fail (AS_IS_RELEASE (release), 0);
 	if (kind >= AS_SIZE_KIND_LAST)
 		return 0;
 	if (priv->sizes == NULL)
@@ -288,6 +292,7 @@ void
 as_release_set_size (AsRelease *release, AsSizeKind kind, guint64 size)
 {
 	AsReleasePrivate *priv = GET_PRIVATE (release);
+	g_return_if_fail (AS_IS_RELEASE (release));
 	if (kind >= AS_SIZE_KIND_LAST)
 		return;
 	as_release_ensure_sizes (release);
@@ -308,6 +313,7 @@ AsUrgencyKind
 as_release_get_urgency (AsRelease *release)
 {
 	AsReleasePrivate *priv = GET_PRIVATE (release);
+	g_return_val_if_fail (AS_IS_RELEASE (release), AS_URGENCY_KIND_UNKNOWN);
 	return priv->urgency;
 }
 
@@ -325,6 +331,7 @@ AsReleaseState
 as_release_get_state (AsRelease *release)
 {
 	AsReleasePrivate *priv = GET_PRIVATE (release);
+	g_return_val_if_fail (AS_IS_RELEASE (release), AS_RELEASE_STATE_UNKNOWN);
 	return priv->state;
 }
 
@@ -342,6 +349,7 @@ AsReleaseKind
 as_release_get_kind (AsRelease *release)
 {
 	AsReleasePrivate *priv = GET_PRIVATE (release);
+	g_return_val_if_fail (AS_IS_RELEASE (release), AS_RELEASE_KIND_UNKNOWN);
 	return priv->kind;
 }
 
@@ -359,6 +367,7 @@ const gchar *
 as_release_get_version (AsRelease *release)
 {
 	AsReleasePrivate *priv = GET_PRIVATE (release);
+	g_return_val_if_fail (AS_IS_RELEASE (release), NULL);
 	return priv->version;
 }
 
@@ -377,6 +386,7 @@ GBytes *
 as_release_get_blob (AsRelease *release, const gchar *filename)
 {
 	AsReleasePrivate *priv = GET_PRIVATE (release);
+	g_return_val_if_fail (AS_IS_RELEASE (release), NULL);
 	g_return_val_if_fail (filename != NULL, NULL);
 	if (priv->blobs == NULL)
 		return NULL;
@@ -397,6 +407,7 @@ GPtrArray *
 as_release_get_locations (AsRelease *release)
 {
 	AsReleasePrivate *priv = GET_PRIVATE (release);
+	g_return_val_if_fail (AS_IS_RELEASE (release), NULL);
 	as_release_ensure_locations (release);
 	return priv->locations;
 }
@@ -415,6 +426,7 @@ const gchar *
 as_release_get_location_default (AsRelease *release)
 {
 	AsReleasePrivate *priv = GET_PRIVATE (release);
+	g_return_val_if_fail (AS_IS_RELEASE (release), NULL);
 	if (priv->locations == NULL)
 		return NULL;
 	if (priv->locations->len == 0)
@@ -436,6 +448,7 @@ GPtrArray *
 as_release_get_checksums (AsRelease *release)
 {
 	AsReleasePrivate *priv = GET_PRIVATE (release);
+	g_return_val_if_fail (AS_IS_RELEASE (release), NULL);
 	as_release_ensure_checksums (release);
 	return priv->checksums;
 }
@@ -458,6 +471,8 @@ as_release_get_checksum_by_fn (AsRelease *release, const gchar *fn)
 	AsReleasePrivate *priv = GET_PRIVATE (release);
 	guint i;
 
+	g_return_val_if_fail (AS_IS_RELEASE (release), NULL);
+
 	for (i = 0; i < priv->checksums->len; i++) {
 		checksum = g_ptr_array_index (priv->checksums, i);
 		if (g_strcmp0 (fn, as_checksum_get_filename (checksum)) == 0)
@@ -484,6 +499,8 @@ as_release_get_checksum_by_target (AsRelease *release, AsChecksumTarget target)
 	AsReleasePrivate *priv = GET_PRIVATE (release);
 	guint i;
 
+	g_return_val_if_fail (AS_IS_RELEASE (release), NULL);
+
 	if (priv->checksums == NULL)
 		return NULL;
 	for (i = 0; i < priv->checksums->len; i++) {
@@ -508,6 +525,7 @@ guint64
 as_release_get_timestamp (AsRelease *release)
 {
 	AsReleasePrivate *priv = GET_PRIVATE (release);
+	g_return_val_if_fail (AS_IS_RELEASE (release), 0);
 	return priv->timestamp;
 }
 
@@ -526,6 +544,7 @@ const gchar *
 as_release_get_description (AsRelease *release, const gchar *locale)
 {
 	AsReleasePrivate *priv = GET_PRIVATE (release);
+	g_return_val_if_fail (AS_IS_RELEASE (release), NULL);
 	if (priv->descriptions == NULL)
 		return NULL;
 	return as_hash_lookup_by_locale (priv->descriptions, locale);
@@ -544,6 +563,7 @@ void
 as_release_set_version (AsRelease *release, const gchar *version)
 {
 	AsReleasePrivate *priv = GET_PRIVATE (release);
+	g_return_if_fail (AS_IS_RELEASE (release));
 	as_ref_string_assign_safe (&priv->version, version);
 }
 
@@ -563,6 +583,7 @@ void
 as_release_set_blob (AsRelease *release, const gchar *filename, GBytes *blob)
 {
 	AsReleasePrivate *priv = GET_PRIVATE (release);
+	g_return_if_fail (AS_IS_RELEASE (release));
 	g_return_if_fail (filename != NULL);
 	g_return_if_fail (blob != NULL);
 
@@ -585,6 +606,7 @@ void
 as_release_set_urgency (AsRelease *release, AsUrgencyKind urgency)
 {
 	AsReleasePrivate *priv = GET_PRIVATE (release);
+	g_return_if_fail (AS_IS_RELEASE (release));
 	priv->urgency = urgency;
 }
 
@@ -601,6 +623,7 @@ void
 as_release_set_kind (AsRelease *release, AsReleaseKind kind)
 {
 	AsReleasePrivate *priv = GET_PRIVATE (release);
+	g_return_if_fail (AS_IS_RELEASE (release));
 	priv->kind = kind;
 }
 
@@ -617,6 +640,7 @@ void
 as_release_set_state (AsRelease *release, AsReleaseState state)
 {
 	AsReleasePrivate *priv = GET_PRIVATE (release);
+	g_return_if_fail (AS_IS_RELEASE (release));
 	priv->state = state;
 }
 
@@ -634,6 +658,8 @@ as_release_add_location (AsRelease *release, const gchar *location)
 {
 	AsReleasePrivate *priv = GET_PRIVATE (release);
 
+	g_return_if_fail (AS_IS_RELEASE (release));
+
 	/* deduplicate */
 	as_release_ensure_locations (release);
 	if (as_ptr_array_find_string (priv->locations, location))
@@ -655,6 +681,7 @@ void
 as_release_add_checksum (AsRelease *release, AsChecksum *checksum)
 {
 	AsReleasePrivate *priv = GET_PRIVATE (release);
+	g_return_if_fail (AS_IS_RELEASE (release));
 	as_release_ensure_checksums (release);
 	g_ptr_array_add (priv->checksums, g_object_ref (checksum));
 }
@@ -672,6 +699,7 @@ void
 as_release_set_timestamp (AsRelease *release, guint64 timestamp)
 {
 	AsReleasePrivate *priv = GET_PRIVATE (release);
+	g_return_if_fail (AS_IS_RELEASE (release));
 	priv->timestamp = timestamp;
 }
 
@@ -691,6 +719,7 @@ as_release_set_description (AsRelease *release,
 			    const gchar *description)
 {
 	AsReleasePrivate *priv = GET_PRIVATE (release);
+	g_return_if_fail (AS_IS_RELEASE (release));
 	if (locale == NULL)
 		locale = "C";
 	if (priv->descriptions == NULL) {
@@ -723,6 +752,8 @@ as_release_node_insert (AsRelease *release, GNode *parent, AsNodeContext *ctx)
 	AsChecksum *checksum;
 	GNode *n;
 
+	g_return_val_if_fail (AS_IS_RELEASE (release), NULL);
+
 	n = as_node_insert (parent, "release", NULL,
 			    AS_NODE_INSERT_FLAG_NONE,
 			    NULL);
@@ -799,6 +830,8 @@ as_release_node_parse (AsRelease *release, GNode *node,
 	GNode *n;
 	const gchar *tmp;
 
+	g_return_val_if_fail (AS_IS_RELEASE (release), FALSE);
+
 	tmp = as_node_get_attribute (node, "timestamp");
 	if (tmp != NULL)
 		as_release_set_timestamp (release, g_ascii_strtoull (tmp, NULL, 10));
@@ -916,6 +949,8 @@ as_release_node_parse_dep11 (AsRelease *release, GNode *node,
 	const gchar *tmp;
 	const gchar *value;
 
+	g_return_val_if_fail (AS_IS_RELEASE (release), FALSE);
+
 	for (n = node->children; n != NULL; n = n->next) {
 		tmp = as_yaml_node_get_key (n);
 		if (g_strcmp0 (tmp, "unix-timestamp") == 0) {
diff --git a/libappstream-glib/as-require.c b/libappstream-glib/as-require.c
index cfaff86..4604e79 100644
--- a/libappstream-glib/as-require.c
+++ b/libappstream-glib/as-require.c
@@ -213,6 +213,7 @@ const gchar *
 as_require_get_version (AsRequire *require)
 {
 	AsRequirePrivate *priv = GET_PRIVATE (require);
+	g_return_val_if_fail (AS_IS_REQUIRE (require), NULL);
 	return priv->version;
 }
 
@@ -230,6 +231,7 @@ const gchar *
 as_require_get_value (AsRequire *require)
 {
 	AsRequirePrivate *priv = GET_PRIVATE (require);
+	g_return_val_if_fail (AS_IS_REQUIRE (require), NULL);
 	return priv->value;
 }
 
@@ -247,6 +249,7 @@ AsRequireKind
 as_require_get_kind (AsRequire *require)
 {
 	AsRequirePrivate *priv = GET_PRIVATE (require);
+	g_return_val_if_fail (AS_IS_REQUIRE (require), AS_REQUIRE_KIND_UNKNOWN);
 	return priv->kind;
 }
 
@@ -263,6 +266,7 @@ void
 as_require_set_kind (AsRequire *require, AsRequireKind kind)
 {
 	AsRequirePrivate *priv = GET_PRIVATE (require);
+	g_return_if_fail (AS_IS_REQUIRE (require));
 	priv->kind = kind;
 }
 
@@ -280,6 +284,7 @@ AsRequireCompare
 as_require_get_compare (AsRequire *require)
 {
 	AsRequirePrivate *priv = GET_PRIVATE (require);
+	g_return_val_if_fail (AS_IS_REQUIRE (require), AS_REQUIRE_COMPARE_UNKNOWN);
 	return priv->compare;
 }
 
@@ -296,6 +301,7 @@ void
 as_require_set_compare (AsRequire *require, AsRequireCompare compare)
 {
 	AsRequirePrivate *priv = GET_PRIVATE (require);
+	g_return_if_fail (AS_IS_REQUIRE (require));
 	priv->compare = compare;
 }
 
@@ -312,6 +318,7 @@ void
 as_require_set_version (AsRequire *require, const gchar *version)
 {
 	AsRequirePrivate *priv = GET_PRIVATE (require);
+	g_return_if_fail (AS_IS_REQUIRE (require));
 	if (priv->version != NULL)
 		as_ref_string_unref (priv->version);
 	priv->version = as_ref_string_new (version);
@@ -330,6 +337,7 @@ void
 as_require_set_value (AsRequire *require, const gchar *value)
 {
 	AsRequirePrivate *priv = GET_PRIVATE (require);
+	g_return_if_fail (AS_IS_REQUIRE (require));
 	if (priv->value != NULL)
 		as_ref_string_unref (priv->value);
 	priv->value = as_ref_string_new (value);
@@ -357,6 +365,8 @@ as_require_version_compare (AsRequire *require,
 	gboolean ret = FALSE;
 	gint rc = 0;
 
+	g_return_val_if_fail (AS_IS_REQUIRE (require), FALSE);
+
 	switch (priv->compare) {
 	case AS_REQUIRE_COMPARE_EQ:
 		rc = as_utils_vercmp (version, priv->version);
@@ -433,6 +443,9 @@ as_require_equal (AsRequire *require1, AsRequire *require2)
 	AsRequirePrivate *priv1 = GET_PRIVATE (require1);
 	AsRequirePrivate *priv2 = GET_PRIVATE (require2);
 
+	g_return_val_if_fail (AS_IS_REQUIRE (require1), FALSE);
+	g_return_val_if_fail (AS_IS_REQUIRE (require2), FALSE);
+
 	/* trivial */
 	if (require1 == require2)
 		return TRUE;
@@ -469,6 +482,8 @@ as_require_node_insert (AsRequire *require, GNode *parent, AsNodeContext *ctx)
 	AsRequirePrivate *priv = GET_PRIVATE (require);
 	GNode *n;
 
+	g_return_val_if_fail (AS_IS_REQUIRE (require), NULL);
+
 	/* don't know what to do here */
 	if (priv->kind == AS_REQUIRE_KIND_UNKNOWN)
 		return NULL;
@@ -506,6 +521,7 @@ as_require_node_parse (AsRequire *require, GNode *node,
 {
 	AsRequirePrivate *priv = GET_PRIVATE (require);
 	const gchar *tmp;
+	g_return_val_if_fail (AS_IS_REQUIRE (require), FALSE);
 	tmp = as_node_get_name (node);
 	if (tmp != NULL)
 		as_require_set_kind (require, as_require_kind_from_string (tmp));
diff --git a/libappstream-glib/as-review.c b/libappstream-glib/as-review.c
index 97f1491..053fe63 100644
--- a/libappstream-glib/as-review.c
+++ b/libappstream-glib/as-review.c
@@ -537,7 +537,7 @@ AsReviewFlags
 as_review_get_flags (AsReview *review)
 {
 	AsReviewPrivate *priv = GET_PRIVATE (review);
-	g_return_val_if_fail (AS_IS_REVIEW (review), 0);
+	g_return_val_if_fail (AS_IS_REVIEW (review), AS_REVIEW_FLAG_NONE);
 	return priv->flags;
 }
 
@@ -905,6 +905,8 @@ as_review_node_parse (AsReview *review, GNode *node,
 	const gchar *tmp;
 	gint itmp;
 
+	g_return_val_if_fail (AS_IS_REVIEW (review), FALSE);
+
 	itmp = as_node_get_attribute_as_int (node, "rating");
 	if (itmp != G_MAXINT)
 		as_review_set_rating (review, itmp);
diff --git a/libappstream-glib/as-screenshot.c b/libappstream-glib/as-screenshot.c
index d4c7245..a4b5ead 100644
--- a/libappstream-glib/as-screenshot.c
+++ b/libappstream-glib/as-screenshot.c
@@ -148,6 +148,7 @@ AsScreenshotKind
 as_screenshot_get_kind (AsScreenshot *screenshot)
 {
 	AsScreenshotPrivate *priv = GET_PRIVATE (screenshot);
+	g_return_val_if_fail (AS_IS_SCREENSHOT (screenshot), AS_SCREENSHOT_KIND_UNKNOWN);
 	return priv->kind;
 }
 
@@ -165,6 +166,7 @@ gint
 as_screenshot_get_priority (AsScreenshot *screenshot)
 {
 	AsScreenshotPrivate *priv = GET_PRIVATE (screenshot);
+	g_return_val_if_fail (AS_IS_SCREENSHOT (screenshot), 0);
 	return priv->priority;
 }
 
@@ -182,6 +184,7 @@ GPtrArray *
 as_screenshot_get_images (AsScreenshot *screenshot)
 {
 	AsScreenshotPrivate *priv = GET_PRIVATE (screenshot);
+	g_return_val_if_fail (AS_IS_SCREENSHOT (screenshot), NULL);
 	return priv->images;
 }
 
@@ -205,6 +208,8 @@ as_screenshot_get_images_for_locale (AsScreenshot *screenshot,
 	GPtrArray *array;
 	guint i;
 
+	g_return_val_if_fail (AS_IS_SCREENSHOT (screenshot), NULL);
+
 	/* user wants a specific locale */
 	array = g_ptr_array_new_with_free_func ((GDestroyNotify) g_object_unref);
 	for (i = 0; i < priv->images->len; i++) {
@@ -303,6 +308,8 @@ as_screenshot_get_source (AsScreenshot *screenshot)
 	AsScreenshotPrivate *priv = GET_PRIVATE (screenshot);
 	guint i;
 
+	g_return_val_if_fail (AS_IS_SCREENSHOT (screenshot), NULL);
+
 	for (i = 0; i < priv->images->len; i++) {
 		im = g_ptr_array_index (priv->images, i);
 		if (as_image_get_kind (im) == AS_IMAGE_KIND_SOURCE)
@@ -326,6 +333,7 @@ const gchar *
 as_screenshot_get_caption (AsScreenshot *screenshot, const gchar *locale)
 {
 	AsScreenshotPrivate *priv = GET_PRIVATE (screenshot);
+	g_return_val_if_fail (AS_IS_SCREENSHOT (screenshot), NULL);
 	if (priv->captions == NULL)
 		return NULL;
 	return as_hash_lookup_by_locale (priv->captions, locale);
@@ -344,6 +352,7 @@ void
 as_screenshot_set_priority (AsScreenshot *screenshot, gint priority)
 {
 	AsScreenshotPrivate *priv = GET_PRIVATE (screenshot);
+	g_return_if_fail (AS_IS_SCREENSHOT (screenshot));
 	priv->priority = priority;
 }
 
@@ -360,6 +369,7 @@ void
 as_screenshot_set_kind (AsScreenshot *screenshot, AsScreenshotKind kind)
 {
 	AsScreenshotPrivate *priv = GET_PRIVATE (screenshot);
+	g_return_if_fail (AS_IS_SCREENSHOT (screenshot));
 	priv->kind = kind;
 }
 
@@ -376,6 +386,7 @@ void
 as_screenshot_add_image (AsScreenshot *screenshot, AsImage *image)
 {
 	AsScreenshotPrivate *priv = GET_PRIVATE (screenshot);
+	g_return_if_fail (AS_IS_SCREENSHOT (screenshot));
 	g_ptr_array_add (priv->images, g_object_ref (image));
 }
 
@@ -395,6 +406,7 @@ as_screenshot_set_caption (AsScreenshot *screenshot,
 			   const gchar *caption)
 {
 	AsScreenshotPrivate *priv = GET_PRIVATE (screenshot);
+	g_return_if_fail (AS_IS_SCREENSHOT (screenshot));
 	if (locale == NULL)
 		locale = "C";
 	as_screenshot_ensure_captions (screenshot);
@@ -425,6 +437,8 @@ as_screenshot_node_insert (AsScreenshot *screenshot,
 	GNode *n;
 	guint i;
 
+	g_return_val_if_fail (AS_IS_SCREENSHOT (screenshot), NULL);
+
 	/* nothing to add */
 	if (priv->images->len == 0)
 		return NULL;
@@ -477,6 +491,8 @@ as_screenshot_node_parse (AsScreenshot *screenshot, GNode *node,
 	gint priority;
 	g_autoptr(GHashTable) captions = NULL;
 
+	g_return_val_if_fail (AS_IS_SCREENSHOT (screenshot), FALSE);
+
 	tmp = as_node_get_attribute (node, "type");
 	if (tmp != NULL) {
 		as_screenshot_set_kind (screenshot,
@@ -601,6 +617,9 @@ as_screenshot_equal (AsScreenshot *screenshot1, AsScreenshot *screenshot2)
 	AsImage *im1;
 	AsImage *im2;
 
+	g_return_val_if_fail (AS_IS_SCREENSHOT (screenshot1), FALSE);
+	g_return_val_if_fail (AS_IS_SCREENSHOT (screenshot2), FALSE);
+
 	/* trivial */
 	if (screenshot1 == screenshot2)
 		return TRUE;
diff --git a/libappstream-glib/as-store.c b/libappstream-glib/as-store.c
index d573e07..0b69ecc 100644
--- a/libappstream-glib/as-store.c
+++ b/libappstream-glib/as-store.c
@@ -282,6 +282,7 @@ void
 as_store_add_filter (AsStore *store, AsAppKind kind)
 {
 	AsStorePrivate *priv = GET_PRIVATE (store);
+	g_return_if_fail (AS_IS_STORE (store));
 	priv->filter |= 1u << kind;
 }
 
@@ -302,6 +303,7 @@ void
 as_store_remove_filter (AsStore *store, AsAppKind kind)
 {
 	AsStorePrivate *priv = GET_PRIVATE (store);
+	g_return_if_fail (AS_IS_STORE (store));
 	priv->filter &= ~(1u << kind);
 }
 
@@ -1016,6 +1018,8 @@ as_store_remove_app (AsStore *store, AsApp *app)
 	AsStorePrivate *priv = GET_PRIVATE (store);
 	GPtrArray *apps;
 
+	g_return_if_fail (AS_IS_STORE (store));
+
 	/* emit before removal */
 	g_signal_emit (store, signals[SIGNAL_APP_REMOVED], 0, app);
 
@@ -1054,6 +1058,8 @@ as_store_remove_app_by_id (AsStore *store, const gchar *id)
 	AsStorePrivate *priv = GET_PRIVATE (store);
 	guint i;
 
+	g_return_if_fail (AS_IS_STORE (store));
+
 	if (!g_hash_table_remove (priv->hash_id, id))
 		return;
 	for (i = 0; i < priv->array->len; i++) {
@@ -1142,6 +1148,8 @@ as_store_add_app (AsStore *store, AsApp *app)
 	const gchar *pkgname;
 	guint i;
 
+	g_return_if_fail (AS_IS_STORE (store));
+
 	/* have we recorded this before? */
 	id = as_app_get_id (app);
 	if (id == NULL) {
@@ -2063,6 +2071,8 @@ as_store_from_file (AsStore *store,
 {
 	AsStorePrivate *priv = GET_PRIVATE (store);
 
+	g_return_val_if_fail (AS_IS_STORE (store), FALSE);
+
 	return as_store_from_file_internal (store, file,
 					    AS_APP_SCOPE_UNKNOWN,
 					    NULL, /* arch */
@@ -2232,6 +2242,8 @@ as_store_remove_apps_with_veto (AsStore *store)
 	AsStorePrivate *priv = GET_PRIVATE (store);
 	_cleanup_uninhibit_ guint32 *tok = NULL;
 
+	g_return_if_fail (AS_IS_STORE (store));
+
 	/* don't shortcut the list as we have to use as_store_remove_app()
 	 * rather than just removing from the GPtrArray */
 	tok = as_store_changed_inhibit (store);
@@ -2274,6 +2286,8 @@ as_store_to_xml (AsStore *store, guint32 flags)
 	gchar version[6];
 	g_autoptr(AsNodeContext) ctx = NULL;
 
+	g_return_val_if_fail (AS_IS_STORE (store), NULL);
+
 	/* check categories of apps about to be written */
 	as_store_check_apps_for_veto (store);
 
@@ -2336,6 +2350,8 @@ as_store_convert_icons (AsStore *store, AsIconKind kind, GError **error)
 	AsApp *app;
 	guint i;
 
+	g_return_val_if_fail (AS_IS_STORE (store), FALSE);
+
 	/* convert application icons */
 	for (i = 0; i < priv->array->len; i++) {
 		app = g_ptr_array_index (priv->array, i);
@@ -2451,6 +2467,7 @@ const gchar *
 as_store_get_origin (AsStore *store)
 {
 	AsStorePrivate *priv = GET_PRIVATE (store);
+	g_return_val_if_fail (AS_IS_STORE (store), NULL);
 	return priv->origin;
 }
 
@@ -2467,6 +2484,7 @@ void
 as_store_set_origin (AsStore *store, const gchar *origin)
 {
 	AsStorePrivate *priv = GET_PRIVATE (store);
+	g_return_if_fail (AS_IS_STORE (store));
 	g_free (priv->origin);
 	priv->origin = g_strdup (origin);
 }
@@ -2486,6 +2504,7 @@ const gchar *
 as_store_get_builder_id (AsStore *store)
 {
 	AsStorePrivate *priv = GET_PRIVATE (store);
+	g_return_val_if_fail (AS_IS_STORE (store), NULL);
 	return priv->builder_id;
 }
 
@@ -2503,6 +2522,7 @@ void
 as_store_set_builder_id (AsStore *store, const gchar *builder_id)
 {
 	AsStorePrivate *priv = GET_PRIVATE (store);
+	g_return_if_fail (AS_IS_STORE (store));
 	g_free (priv->builder_id);
 	priv->builder_id = g_strdup (builder_id);
 }
@@ -2520,6 +2540,7 @@ void
 as_store_set_destdir (AsStore *store, const gchar *destdir)
 {
 	AsStorePrivate *priv = GET_PRIVATE (store);
+	g_return_if_fail (AS_IS_STORE (store));
 	g_free (priv->destdir);
 	priv->destdir = g_strdup (destdir);
 }
@@ -2538,6 +2559,7 @@ const gchar *
 as_store_get_destdir (AsStore *store)
 {
 	AsStorePrivate *priv = GET_PRIVATE (store);
+	g_return_val_if_fail (AS_IS_STORE (store), NULL);
 	return priv->destdir;
 }
 
@@ -2555,6 +2577,7 @@ gdouble
 as_store_get_api_version (AsStore *store)
 {
 	AsStorePrivate *priv = GET_PRIVATE (store);
+	g_return_val_if_fail (AS_IS_STORE (store), 0.0);
 	return priv->api_version;
 }
 
@@ -2571,6 +2594,7 @@ void
 as_store_set_api_version (AsStore *store, gdouble api_version)
 {
 	AsStorePrivate *priv = GET_PRIVATE (store);
+	g_return_if_fail (AS_IS_STORE (store));
 	priv->api_version = api_version;
 }
 
@@ -2588,6 +2612,7 @@ guint32
 as_store_get_add_flags (AsStore *store)
 {
 	AsStorePrivate *priv = GET_PRIVATE (store);
+	g_return_val_if_fail (AS_IS_STORE (store), 0);
 	return priv->add_flags;
 }
 
@@ -2607,6 +2632,7 @@ void
 as_store_set_add_flags (AsStore *store, guint32 add_flags)
 {
 	AsStorePrivate *priv = GET_PRIVATE (store);
+	g_return_if_fail (AS_IS_STORE (store));
 	priv->add_flags = add_flags;
 }
 
@@ -2624,6 +2650,7 @@ guint32
 as_store_get_watch_flags (AsStore *store)
 {
 	AsStorePrivate *priv = GET_PRIVATE (store);
+	g_return_val_if_fail (AS_IS_STORE (store), AS_STORE_WATCH_FLAG_NONE);
 	return priv->watch_flags;
 }
 
@@ -2640,6 +2667,7 @@ void
 as_store_set_watch_flags (AsStore *store, guint32 watch_flags)
 {
 	AsStorePrivate *priv = GET_PRIVATE (store);
+	g_return_if_fail (AS_IS_STORE (store));
 	priv->watch_flags = watch_flags;
 }
 
@@ -3157,6 +3185,8 @@ as_store_load_search_cache (AsStore *store)
 	GThreadPool *pool;
 	g_autoptr(AsProfileTask) ptask = NULL;
 
+	g_return_if_fail (AS_IS_STORE (store));
+
 	/* profile */
 	ptask = as_profile_start_literal (priv->profile,
 					  "AsStore:load-token-cache");
@@ -3193,6 +3223,8 @@ as_store_load (AsStore *store, guint32 flags, GCancellable *cancellable, GError
 	g_autoptr(AsProfileTask) ptask = NULL;
 	_cleanup_uninhibit_ guint32 *tok = NULL;
 
+	g_return_val_if_fail (AS_IS_STORE (store), FALSE);
+
 	/* profile */
 	ptask = as_profile_start_literal (priv->profile, "AsStore:load");
 	g_assert (ptask != NULL);
@@ -3548,6 +3580,7 @@ void
 as_store_set_search_match (AsStore *store, guint16 search_match)
 {
 	AsStorePrivate *priv = GET_PRIVATE (store);
+	g_return_if_fail (AS_IS_STORE (store));
 	priv->search_match = search_match;
 }
 
@@ -3566,6 +3599,7 @@ guint16
 as_store_get_search_match (AsStore *store)
 {
 	AsStorePrivate *priv = GET_PRIVATE (store);
+	g_return_val_if_fail (AS_IS_STORE (store), 0);
 	return priv->search_match;
 }
 
diff --git a/libappstream-glib/as-suggest.c b/libappstream-glib/as-suggest.c
index 174d745..039a950 100644
--- a/libappstream-glib/as-suggest.c
+++ b/libappstream-glib/as-suggest.c
@@ -129,6 +129,7 @@ GPtrArray *
 as_suggest_get_ids (AsSuggest *suggest)
 {
 	AsSuggestPrivate *priv = GET_PRIVATE (suggest);
+	g_return_val_if_fail (AS_IS_SUGGEST (suggest), NULL);
 	return priv->ids;
 }
 
@@ -146,6 +147,7 @@ AsSuggestKind
 as_suggest_get_kind (AsSuggest *suggest)
 {
 	AsSuggestPrivate *priv = GET_PRIVATE (suggest);
+	g_return_val_if_fail (AS_IS_SUGGEST (suggest), AS_SUGGEST_KIND_UNKNOWN);
 	return priv->kind;
 }
 
@@ -162,6 +164,7 @@ void
 as_suggest_set_kind (AsSuggest *suggest, AsSuggestKind kind)
 {
 	AsSuggestPrivate *priv = GET_PRIVATE (suggest);
+	g_return_if_fail (AS_IS_SUGGEST (suggest));
 	priv->kind = kind;
 }
 
@@ -178,6 +181,7 @@ void
 as_suggest_add_id (AsSuggest *suggest, const gchar *id)
 {
 	AsSuggestPrivate *priv = GET_PRIVATE (suggest);
+	g_return_if_fail (AS_IS_SUGGEST (suggest));
 	g_ptr_array_add (priv->ids, as_ref_string_new (id));
 }
 
@@ -200,6 +204,8 @@ as_suggest_node_insert (AsSuggest *suggest, GNode *parent, AsNodeContext *ctx)
 	GNode *n;
 	guint i;
 
+	g_return_val_if_fail (AS_IS_SUGGEST (suggest), NULL);
+
 	n = as_node_insert (parent, "suggests", NULL,
 			    AS_NODE_INSERT_FLAG_NONE,
 			    NULL);
diff --git a/libappstream-glib/as-translation.c b/libappstream-glib/as-translation.c
index 60c07f2..883dddd 100644
--- a/libappstream-glib/as-translation.c
+++ b/libappstream-glib/as-translation.c
@@ -130,6 +130,7 @@ const gchar *
 as_translation_get_id (AsTranslation *translation)
 {
 	AsTranslationPrivate *priv = GET_PRIVATE (translation);
+	g_return_val_if_fail (AS_IS_TRANSLATION (translation), NULL);
 	return priv->id;
 }
 
@@ -147,6 +148,7 @@ AsTranslationKind
 as_translation_get_kind (AsTranslation *translation)
 {
 	AsTranslationPrivate *priv = GET_PRIVATE (translation);
+	g_return_val_if_fail (AS_IS_TRANSLATION (translation), AS_TRANSLATION_KIND_UNKNOWN);
 	return priv->kind;
 }
 
@@ -163,6 +165,7 @@ void
 as_translation_set_id (AsTranslation *translation, const gchar *id)
 {
 	AsTranslationPrivate *priv = GET_PRIVATE (translation);
+	g_return_if_fail (AS_IS_TRANSLATION (translation));
 	as_ref_string_assign_safe (&priv->id, id);
 }
 
@@ -179,6 +182,7 @@ void
 as_translation_set_kind (AsTranslation *translation, AsTranslationKind kind)
 {
 	AsTranslationPrivate *priv = GET_PRIVATE (translation);
+	g_return_if_fail (AS_IS_TRANSLATION (translation));
 	priv->kind = kind;
 }
 
@@ -200,6 +204,8 @@ as_translation_node_insert (AsTranslation *translation, GNode *parent, AsNodeCon
 	AsTranslationPrivate *priv = GET_PRIVATE (translation);
 	GNode *n;
 
+	g_return_val_if_fail (AS_IS_TRANSLATION (translation), NULL);
+
 	/* invalid */
 	if (priv->kind == AS_TRANSLATION_KIND_UNKNOWN)
 		return NULL;
@@ -231,6 +237,8 @@ as_translation_node_parse (AsTranslation *translation, GNode *node,
 	AsTranslationPrivate *priv = GET_PRIVATE (translation);
 	const gchar *tmp;
 
+	g_return_val_if_fail (AS_IS_TRANSLATION (translation), FALSE);
+
 	tmp = as_node_get_attribute (node, "type");
 	as_translation_set_kind (translation, as_translation_kind_from_string (tmp));
 	as_ref_string_assign (&priv->id, as_node_get_data_as_refstr (node));
@@ -251,16 +259,18 @@ as_translation_node_parse (AsTranslation *translation, GNode *node,
  * Since: 0.5.8
  **/
 gboolean
-as_translation_node_parse_dep11 (AsTranslation *im, GNode *node,
+as_translation_node_parse_dep11 (AsTranslation *translation, GNode *node,
 				 AsNodeContext *ctx, GError **error)
 {
 	GNode *n;
 	const gchar *tmp;
 
+	g_return_val_if_fail (AS_IS_TRANSLATION (translation), FALSE);
+
 	for (n = node->children; n != NULL; n = n->next) {
 		tmp = as_yaml_node_get_key (n);
 		if (g_strcmp0 (tmp, "id") == 0)
-			as_translation_set_id (im, as_yaml_node_get_value (n));
+			as_translation_set_id (translation, as_yaml_node_get_value (n));
 	}
 	return TRUE;
 }