--- a/widget/gtk/nsAppShell.cpp
+++ b/widget/gtk/nsAppShell.cpp
@@ -44,17 +44,17 @@ PollWrapper(GPollFD *ufds, guint nfsd, g
     mozilla::HangMonitor::NotifyActivity();
     return result;
 }
 
 #if MOZ_WIDGET_GTK == 3
 // For bug 726483.
 static decltype(GtkContainerClass::check_resize) sReal_gtk_window_check_resize;
 
-void
+static void
 wrap_gtk_window_check_resize(GtkContainer *container)
 {
     GdkWindow* gdk_window = gtk_widget_get_window(&container->widget);
     if (gdk_window) {
         g_object_ref(gdk_window);
     }
 
     sReal_gtk_window_check_resize(container);