diff --git a/src/transparency_gui.cpp b/src/transparency_gui.cpp
--- a/src/transparency_gui.cpp
+++ b/src/transparency_gui.cpp
@@ -36,7 +36,7 @@ class TransparenciesWindow : public Wind
 	};
 
 public:
-	TransparenciesWindow(const WindowDesc *desc, void *data, int window_number) : Window(desc, data, window_number)
+	TransparenciesWindow(const WindowDesc *desc, int window_number) : Window(desc, window_number)
 	{
 		this->FindWindowPlacementAndResize(desc);
 	}