diff --git a/tests/app/tests/test_webpack.py b/tests/app/tests/test_webpack.py
index c7ec3b06..99ed787b 100644
--- a/tests/app/tests/test_webpack.py
+++ b/tests/app/tests/test_webpack.py
@@ -160,7 +160,7 @@ def test_missing_bundle(self):
         try:
             get_loader(DEFAULT_CONFIG).get_bundle(missing_bundle_name)
         except WebpackBundleLookupError as e:
-            self.assertIn('Cannot resolve bundle {}'.format(missing_bundle_name), str(e))
+            self.assertIn('Cannot resolve bundle {0}'.format(missing_bundle_name), str(e))
 
     def test_missing_stats_file(self):
         stats_file = settings.WEBPACK_LOADER[DEFAULT_CONFIG]['STATS_FILE']