diff --git a/src/widgets/help_widget.h b/src/widgets/help_widget.h
--- a/src/widgets/help_widget.h
+++ b/src/widgets/help_widget.h
@@ -11,7 +11,7 @@
 #define WIDGETS_HELP_WIDGET_H
 
 /** Widgets of the #HelpWindow class. */
-enum HelpWindowWidgets {
+enum HelpWindowWidgets : WidgetID {
 	WID_HW_README,
 	WID_HW_CHANGELOG,
 	WID_HW_KNOWN_BUGS,