diff --git a/gtk/gtkoffscreenwindow.h b/gtk/gtkoffscreenwindow.h
index 518b8df261..a706e6704c 100644
--- a/gtk/gtkoffscreenwindow.h
+++ b/gtk/gtkoffscreenwindow.h
@@ -18,7 +18,7 @@
  *          Alexander Larsson <alexl@redhat.com>
  */
 
-#if defined(GTK_DISABLE_SINGLE_INCLUDES) && !defined (__GTK_H_INSIDE__) && !defined (GTK_COMPILATION)
+#if !defined (__GTK_H_INSIDE__) && !defined (GTK_COMPILATION)
 #error "Only <gtk/gtk.h> can be included directly."
 #endif
 
@@ -49,9 +49,9 @@ struct _GtkOffscreenWindowClass
   GtkWindowClass parent_class;
 };
 
-GType      gtk_offscreen_window_get_type () G_GNUC_CONST;
+GType      gtk_offscreen_window_get_type   (void) G_GNUC_CONST;
 
-GtkWidget *gtk_offscreen_window_new ();
+GtkWidget *gtk_offscreen_window_new        (void);
 GdkPixmap *gtk_offscreen_window_get_pixmap (GtkOffscreenWindow *offscreen);
 GdkPixbuf *gtk_offscreen_window_get_pixbuf (GtkOffscreenWindow *offscreen);