diff --git a/src/widgets/dropdown_func.h b/src/widgets/dropdown_func.h
--- a/src/widgets/dropdown_func.h
+++ b/src/widgets/dropdown_func.h
@@ -13,6 +13,6 @@
 #include "../window_gui.h"
 
 /* Show drop down menu containing a fixed list of strings */
-void ShowDropDownMenu(Window *w, const StringID *strings, int selected, int button, uint32_t disabled_mask, uint32_t hidden_mask, uint width = 0);
+void ShowDropDownMenu(Window *w, const StringID *strings, int selected, WidgetID button, uint32_t disabled_mask, uint32_t hidden_mask, uint width = 0);
 
 #endif /* WIDGETS_DROPDOWN_FUNC_H */