diff --git a/Tests/t_cext.py b/Tests/t_cext.py
index 8778bb4..1da4116 100644
--- a/Tests/t_cext.py
+++ b/Tests/t_cext.py
@@ -692,6 +692,17 @@ def test_invalid_filter(self):
         else:
             self.fail("expected FILTER_ERROR, got %r" % r)
 
+    def test_invalid_credentials(self):
+        l = self._open_conn(bind=False)
+        # search with invalid filter
+        try:
+            m = l.simple_bind(self.server.root_dn, self.server.root_pw+'wrong')
+            r = l.result4(m, _ldap.MSG_ALL, self.timeout)
+        except _ldap.INVALID_CREDENTIALS:
+            pass
+        else:
+            self.fail("expected INVALID_CREDENTIALS, got %r" % r)
+
 
 if __name__ == '__main__':
     unittest.main()