diff --git a/python/pydiffx/tests/testcases.py b/python/pydiffx/tests/testcases.py
index fdcbf99..6421569 100644
--- a/python/pydiffx/tests/testcases.py
+++ b/python/pydiffx/tests/testcases.py
@@ -65,5 +65,5 @@ def assertMultiLineBytesEqual(self, first, second, line_endings='unix'):
 
     @contextmanager
     def assertRaisesMessage(self, exception, message):
-        with self.assertRaisesRegexp(exception, re.escape(message)):
+        with self.assertRaises(exception, msg=message):
             yield