diff --git a/src/transparency_gui.cpp b/src/transparency_gui.cpp
--- a/src/transparency_gui.cpp
+++ b/src/transparency_gui.cpp
@@ -155,7 +155,7 @@ static const WindowDesc _transparency_de
 	WDP_ALIGN_TBR, 94, 219, 49, 219, 49,
 	WC_TRANSPARENCY_TOOLBAR, WC_NONE,
 	WDF_STD_TOOLTIPS | WDF_STD_BTN | WDF_DEF_WIDGET | WDF_STICKY_BUTTON,
-	NULL, _nested_transparency_widgets, lengthof(_nested_transparency_widgets)
+	_nested_transparency_widgets, lengthof(_nested_transparency_widgets)
 );
 
 void ShowTransparencyToolbar()