diff --git a/hydra-gtk/src/callbacks.h b/hydra-gtk/src/callbacks.h
index dd213fa..e1084a0 100755
--- a/hydra-gtk/src/callbacks.h
+++ b/hydra-gtk/src/callbacks.h
@@ -8,7 +8,7 @@ void on_about1_activate(GtkMenuItem * menuitem, gpointer user_data);
 
 void on_btnStart_clicked(GtkButton * button, gpointer user_data);
 
-void on_wndMain_destroy(GtkObject * object, gpointer user_data);
+void on_wndMain_destroy(GtkWidget * object, gpointer user_data);
 
 void on_btnStop_clicked(GtkButton * button, gpointer user_data);