diff --git a/gtk/gtkmenubutton.h b/gtk/gtkmenubutton.h
index f03e8a9bbd..f8cb55f349 100644
--- a/gtk/gtkmenubutton.h
+++ b/gtk/gtkmenubutton.h
@@ -66,7 +66,7 @@ GtkWidget   *gtk_menu_button_new            (void);
 
 GDK_AVAILABLE_IN_3_6
 void         gtk_menu_button_set_popup      (GtkMenuButton *menu_button,
-                                             GtkWidget     *menu);
+                                             GtkWidget     *popup);
 GDK_AVAILABLE_IN_3_6
 GtkMenu     *gtk_menu_button_get_popup      (GtkMenuButton *menu_button);