diff --git a/src/viewport_gui.cpp b/src/viewport_gui.cpp
--- a/src/viewport_gui.cpp
+++ b/src/viewport_gui.cpp
@@ -168,7 +168,7 @@ static const WindowDesc _extra_view_port
 	WDP_AUTO, WDP_AUTO, 300, 68, 300, 268,
 	WC_EXTRA_VIEW_PORT, WC_NONE,
 	WDF_STD_TOOLTIPS | WDF_STD_BTN | WDF_DEF_WIDGET | WDF_UNCLICK_BUTTONS | WDF_STICKY_BUTTON | WDF_RESIZABLE,
-	NULL, _nested_extra_view_port_widgets, lengthof(_nested_extra_view_port_widgets)
+	_nested_extra_view_port_widgets, lengthof(_nested_extra_view_port_widgets)
 );
 
 void ShowExtraViewPortWindow(TileIndex tile)