diff --git a/tools/test-backend b/tools/test-backend
index 8f7c83fa0f..7f29043d59 100755
--- a/tools/test-backend
+++ b/tools/test-backend
@@ -174,7 +174,7 @@ if __name__ == "__main__":
     templates_not_rendered = test_runner.get_shallow_tested_templates()
     if templates_not_rendered:
         missed_count = len(templates_not_rendered)
-        print("\nError: %s templates have no tests!".format(missed_count))
+        print("\nError: %s templates have no tests!" % (missed_count,))
         for template in templates_not_rendered:
             print('  {}'.format(template))
         failures = True