diff --git a/django/contrib/admin/widgets.py b/django/contrib/admin/widgets.py
index 81c8ebf3a0..9f8b62041d 100644
--- a/django/contrib/admin/widgets.py
+++ b/django/contrib/admin/widgets.py
@@ -156,6 +156,8 @@ class ManyToManyRawIdWidget(ForeignKeyRawIdWidget):
     in a <select multiple> box.
     """
     def render(self, name, value, attrs=None):
+        if attrs is None:
+            attrs = {}
         attrs['class'] = 'vManyToManyRawIdAdminField'
         if value:
             value = ','.join([force_unicode(v) for v in value])
diff --git a/tests/regressiontests/admin_widgets/models.py b/tests/regressiontests/admin_widgets/models.py
index 20c0df6ee8..89450547ab 100644
--- a/tests/regressiontests/admin_widgets/models.py
+++ b/tests/regressiontests/admin_widgets/models.py
@@ -133,6 +133,8 @@ HTML escaped.
 >>> w = ManyToManyRawIdWidget(rel)
 >>> print conditional_escape(w.render('test', [m1.pk, m2.pk], attrs={}))
 <input type="text" name="test" value="1,2" class="vManyToManyRawIdAdminField" /><a href="../../../admin_widgets/member/" class="related-lookup" id="lookup_id_test" onclick="return showRelatedObjectLookupPopup(this);"> <img src="%(ADMIN_MEDIA_PREFIX)simg/admin/selector-search.gif" width="16" height="16" alt="Lookup" /></a>
+>>> print conditional_escape(w.render('test', [m1.pk]))
+<input type="text" name="test" value="1" class="vManyToManyRawIdAdminField" /><a href="../../../admin_widgets/member/" class="related-lookup" id="lookup_id_test" onclick="return showRelatedObjectLookupPopup(this);"> <img src="%(ADMIN_MEDIA_PREFIX)simg/admin/selector-search.gif" width="16" height="16" alt="Lookup" /></a>
 >>> w._has_changed(None, None)
 False
 >>> w._has_changed([], None)