4 files changed, 16 insertions, 5 deletions
diff --git a/embed.fnc b/embed.fnc
index 19b6b6bec5..986c89383f 100644
--- a/embed.fnc
+++ b/embed.fnc
@@ -1212,7 +1212,7 @@ pMd	|SV*	|sv_2num	|NN SV *const sv
 Amb	|char*	|sv_2pv		|NULLOK SV *sv|NULLOK STRLEN *lp
 Apd	|char*	|sv_2pv_flags	|NULLOK SV *const sv|NULLOK STRLEN *const lp|const I32 flags
 Apd	|char*	|sv_2pvutf8	|NN SV *sv|NULLOK STRLEN *const lp
-Apd	|char*	|sv_2pvbyte	|NN SV *const sv|NULLOK STRLEN *const lp
+Apd	|char*	|sv_2pvbyte	|NN SV *sv|NULLOK STRLEN *const lp
 Ap	|char*	|sv_pvn_nomg	|NN SV* sv|NULLOK STRLEN* lp
 Amb	|UV	|sv_2uv		|NULLOK SV *sv
 Apd	|UV	|sv_2uv_flags	|NULLOK SV *const sv|const I32 flags
diff --git a/ext/XS-APItest/t/svpv.t b/ext/XS-APItest/t/svpv.t
index e98df08486..914b585075 100644
--- a/ext/XS-APItest/t/svpv.t
+++ b/ext/XS-APItest/t/svpv.t
@@ -1,6 +1,6 @@
 #!perl -w
 
-use Test::More tests => 16;
+use Test::More tests => 18;
 
 use XS::APItest;
 
@@ -17,3 +17,9 @@ for my $func ('SvPVbyte', 'SvPVutf8') {
  is &$func($^V), "$^V", "$func(\$ro_ref)";
  is ref\$^V, 'REF', "$func(\$ro_ref) does not flatten the ref";
 }
+
+eval 'SvPVbyte(*{chr 256})';
+like $@, qr/^Wide character/, 'SvPVbyte fails on Unicode glob';
+package r { use overload '""' => sub { substr "\x{100}\xff", -1 } }
+is SvPVbyte(bless [], r::), "\xff",
+  'SvPVbyte on ref returning downgradable utf8 string';
diff --git a/proto.h b/proto.h
index 4f95c42138..528f0a74e7 100644
--- a/proto.h
+++ b/proto.h
@@ -3716,7 +3716,7 @@ PERL_CALLCONV char*	Perl_sv_2pv_flags(pTHX_ SV *const sv, STRLEN *const lp, cons
 #define PERL_ARGS_ASSERT_SV_2PV_NOLEN	\
 	assert(sv)
 
-PERL_CALLCONV char*	Perl_sv_2pvbyte(pTHX_ SV *const sv, STRLEN *const lp)
+PERL_CALLCONV char*	Perl_sv_2pvbyte(pTHX_ SV *sv, STRLEN *const lp)
 			__attribute__nonnull__(pTHX_1);
 #define PERL_ARGS_ASSERT_SV_2PVBYTE	\
 	assert(sv)
diff --git a/sv.c b/sv.c
index 4b37aabbff..f53ad12139 100644
--- a/sv.c
+++ b/sv.c
@@ -3029,11 +3029,16 @@ Usually accessed via the C<SvPVbyte> macro.
 */
 
 char *
-Perl_sv_2pvbyte(pTHX_ register SV *const sv, STRLEN *const lp)
+Perl_sv_2pvbyte(pTHX_ register SV *sv, STRLEN *const lp)
 {
     PERL_ARGS_ASSERT_SV_2PVBYTE;
 
-    SvGETMAGIC(sv);
+    if ((SvTHINKFIRST(sv) && !SvIsCOW(sv)) || isGV_with_GP(sv)) {
+	SV *sv2 = sv_newmortal();
+	sv_copypv(sv2,sv);
+	sv = sv2;
+    }
+    else SvGETMAGIC(sv);
     sv_utf8_downgrade(sv,0);
     return lp ? SvPV_nomg(sv,*lp) : SvPV_nomg_nolen(sv);
 }