diff --git a/libnotify/notification.h b/libnotify/notification.h
index 1a6670c..383c918 100644
--- a/libnotify/notification.h
+++ b/libnotify/notification.h
@@ -76,7 +76,9 @@ typedef enum
 
 } NotifyUrgency;
 
-typedef void (*NotifyActionCallback)(NotifyNotification *, gchar *, gpointer);
+typedef void (*NotifyActionCallback)(NotifyNotification *notification,
+									 gchar *action,
+									 gpointer user_data);
 
 #define NOTIFY_ACTION_CALLBACK(func) ((NotifyActionCallback)(func))