diff --git a/src/transparency_gui.cpp b/src/transparency_gui.cpp
--- a/src/transparency_gui.cpp
+++ b/src/transparency_gui.cpp
@@ -39,7 +39,7 @@ public:
 		this->DrawWidgets();
 	}
 
-	void DrawWidget(const Rect &r, int widget) const override
+	void DrawWidget(const Rect &r, WidgetID widget) const override
 	{
 		switch (widget) {
 			case WID_TT_SIGNS:
@@ -51,13 +51,13 @@ public:
 			case WID_TT_STRUCTURES:
 			case WID_TT_CATENARY:
 			case WID_TT_TEXT: {
-				uint i = widget - WID_TT_BEGIN;
+				int i = widget - WID_TT_BEGIN;
 				if (HasBit(_transparency_lock, i)) DrawSprite(SPR_LOCK, PAL_NONE, r.left + WidgetDimensions::scaled.fullbevel.left, r.top + WidgetDimensions::scaled.fullbevel.top);
 				break;
 			}
 			case WID_TT_BUTTONS: {
 				const Rect fr = r.Shrink(WidgetDimensions::scaled.framerect);
-				for (uint i = WID_TT_BEGIN; i < WID_TT_END; i++) {
+				for (WidgetID i = WID_TT_BEGIN; i < WID_TT_END; i++) {
 					if (i == WID_TT_TEXT) continue; // Loading and cost/income text has no invisibility button.
 
 					const Rect wr = this->GetWidget<NWidgetBase>(i)->GetCurrentRect().Shrink(WidgetDimensions::scaled.fullbevel);
@@ -69,7 +69,7 @@ public:
 		}
 	}
 
-	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_TT_BEGIN && widget < WID_TT_END) {
 			if (_ctrl_pressed) {
@@ -119,7 +119,7 @@ public:
 	void OnInvalidateData([[maybe_unused]] int data = 0, [[maybe_unused]] bool gui_scope = true) override
 	{
 		if (!gui_scope) return;
-		for (uint i = WID_TT_BEGIN; i < WID_TT_END; i++) {
+		for (WidgetID i = WID_TT_BEGIN; i < WID_TT_END; i++) {
 			this->SetWidgetLoweredState(i, IsTransparencySet((TransparencyOption)(i - WID_TT_BEGIN)));
 		}
 	}