diff --git a/tools/check-templates b/tools/check-templates
index 427c7872ea..9369d22b28 100755
--- a/tools/check-templates
+++ b/tools/check-templates
@@ -182,7 +182,7 @@ def get_html_tag(text, i):
 def check_our_files():
     parser = optparse.OptionParser()
     parser.add_option('--modified', '-m',
-        action='store_true',
+        action='store_true', default=False,
         help='Only check modified files')
     (options, _) = parser.parse_args()