diff --git a/include/wx/gtk/window.h b/include/wx/gtk/window.h
index 2d37388a06..f5d03415ca 100644
--- a/include/wx/gtk/window.h
+++ b/include/wx/gtk/window.h
@@ -185,6 +185,7 @@ public:
     // This is called when capture is taken from the window. It will
     // fire off capture lost events.
     void GTKReleaseMouseAndNotify();
+    static void GTKHandleCaptureLost();
 
     GdkWindow* GTKGetDrawingWindow() const;