diff --git a/gtk/gtkscalebutton.h b/gtk/gtkscalebutton.h
index 4bbd49537e..f08dfb98f9 100644
--- a/gtk/gtkscalebutton.h
+++ b/gtk/gtkscalebutton.h
@@ -63,7 +63,7 @@ struct _GtkScaleButton
   GtkWidget *GSEAL(minus_button);
 
   /*< private >*/
-  GtkScaleButtonPrivate *priv;
+  GtkScaleButtonPrivate *GSEAL (priv);
 };
 
 struct _GtkScaleButtonClass