diff --git a/flask/testsuite/__init__.py b/flask/testsuite/__init__.py
index 88cd4d88..89b8cec1 100644
--- a/flask/testsuite/__init__.py
+++ b/flask/testsuite/__init__.py
@@ -154,6 +154,13 @@ class FlaskTestCase(unittest.TestCase):
     def assert_not_in(self, x, y):
         self.assertNotIn(x, y)
 
+    if sys.version_info[:2] == (2, 6):
+        def assertIn(self, x, y):
+            assert x in y, "%r unexpectedly not in %r" % (x, y)
+
+        def assertNotIn(self, x, y):
+            assert x not in y, "%r unexpectedly in %r" % (x, y)
+
 
 class _ExceptionCatcher(object):