- _literal_as_text raises if the incoming arg is not a Visitable or basestring.

[ticket:1847]

1 files changed, 3 insertions, 1 deletions

diff --git a/lib/sqlalchemy/sql/expression.py b/lib/sqlalchemy/sql/expression.py
index ede3235c5..3cfe0a14c 100644
--- a/lib/sqlalchemy/sql/expression.py
+++ b/lib/sqlalchemy/sql/expression.py
@@ -1056,8 +1056,10 @@ def _column_as_key(element):
 def _literal_as_text(element):
     if hasattr(element, '__clause_element__'):
         return element.__clause_element__()
-    elif not isinstance(element, Visitable):
+    elif isinstance(element, basestring):
         return _TextClause(unicode(element))
+    elif not isinstance(element, Visitable):
+        raise exc.ArgumentError("SQL expression object or string expected.")
     else:
         return element