diff --git a/tests/test_titles.py b/tests/test_titles.py
index 669d7b9..84702c4 100644
--- a/tests/test_titles.py
+++ b/tests/test_titles.py
@@ -11,6 +11,7 @@
 # under the License.
 
 import glob
+import os
 import re
 
 import docutils.core
@@ -90,6 +91,8 @@ class TestTitles(testtools.TestCase):
         for file in files:
             if file.endswith('~'):
                 continue
+            if os.path.isdir(file):
+                continue
             self.assertTrue(
                 file.endswith(".rst") or file.endswith(".json"),
                 "guideline file must use 'rst' or 'json'"