diff --git a/git-auto-commit-mode.el b/git-auto-commit-mode.el
index 2cd627f..99d4eb0 100644
--- a/git-auto-commit-mode.el
+++ b/git-auto-commit-mode.el
@@ -140,7 +140,7 @@ Default to FILENAME."
     (if (not gac-ask-for-summary-p)
         (if gac-default-message
             (if (functionp gac-default-message)
-                (gac-default-message)
+                (funcall gac-default-message filename)
               gac-default-message)
           relative-filename)
         (or gac-default-message relative-filename)