diff --git a/src/bootstrap_gui.cpp b/src/bootstrap_gui.cpp
--- a/src/bootstrap_gui.cpp
+++ b/src/bootstrap_gui.cpp
@@ -57,7 +57,7 @@ public:
 		ResizeWindow(this, _screen.width, _screen.height);
 	}
 
-	void DrawWidget(const Rect &r, int) const override
+	void DrawWidget(const Rect &r, WidgetID) const override
 	{
 		GfxFillRect(r.left, r.top, r.right, r.bottom, 4, FILLRECT_OPAQUE);
 		GfxFillRect(r.left, r.top, r.right, r.bottom, 0, FILLRECT_CHECKER);
@@ -97,7 +97,7 @@ public:
 		this->Window::Close();
 	}
 
-	void UpdateWidgetSize(int widget, Dimension *size, [[maybe_unused]] const Dimension &padding, [[maybe_unused]] Dimension *fill, [[maybe_unused]] Dimension *resize) override
+	void UpdateWidgetSize(WidgetID widget, Dimension *size, [[maybe_unused]] const Dimension &padding, [[maybe_unused]] Dimension *fill, [[maybe_unused]] Dimension *resize) override
 	{
 		if (widget == WID_BEM_MESSAGE) {
 			*size = GetStringBoundingBox(STR_MISSING_GRAPHICS_ERROR);
@@ -106,14 +106,14 @@ public:
 		}
 	}
 
-	void DrawWidget(const Rect &r, int widget) const override
+	void DrawWidget(const Rect &r, WidgetID widget) const override
 	{
 		if (widget == WID_BEM_MESSAGE) {
 			DrawStringMultiLine(r.Shrink(WidgetDimensions::scaled.frametext), STR_MISSING_GRAPHICS_ERROR, TC_FROMSTRING, SA_CENTER);
 		}
 	}
 
-	void OnClick([[maybe_unused]] Point pt, int widget, [[maybe_unused]] int click_count) override
+	void OnClick([[maybe_unused]] Point pt, WidgetID widget, [[maybe_unused]] int click_count) override
 	{
 		if (widget == WID_BEM_QUIT) {
 			_exit_game = true;
@@ -211,7 +211,7 @@ public:
 		this->Window::Close();
 	}
 
-	void UpdateWidgetSize(int widget, Dimension *size, [[maybe_unused]] const Dimension &padding, [[maybe_unused]] Dimension *fill, [[maybe_unused]] Dimension *resize) override
+	void UpdateWidgetSize(WidgetID widget, Dimension *size, [[maybe_unused]] const Dimension &padding, [[maybe_unused]] Dimension *fill, [[maybe_unused]] Dimension *resize) override
 	{
 		/* We cache the button size. This is safe as no reinit can happen here. */
 		if (this->button_size.width == 0) {
@@ -234,14 +234,14 @@ public:
 		}
 	}
 
-	void DrawWidget(const Rect &r, int widget) const override
+	void DrawWidget(const Rect &r, WidgetID widget) const override
 	{
 		if (widget != WID_BAFD_QUESTION) return;
 
 		DrawStringMultiLine(r.Shrink(WidgetDimensions::scaled.frametext), STR_MISSING_GRAPHICS_SET_MESSAGE, TC_FROMSTRING, SA_CENTER);
 	}
 
-	void OnClick([[maybe_unused]] Point pt, int widget, [[maybe_unused]] int click_count) override
+	void OnClick([[maybe_unused]] Point pt, WidgetID widget, [[maybe_unused]] int click_count) override
 	{
 		switch (widget) {
 			case WID_BAFD_YES: