diff --git a/src/airport_gui.cpp b/src/airport_gui.cpp
--- a/src/airport_gui.cpp
+++ b/src/airport_gui.cpp
@@ -139,8 +139,8 @@ void ShowBuildAirToolbar()
 {
 	if (!IsValidPlayer(_current_player)) return;
 
-	DeleteWindowById(WC_BUILD_TOOLBAR, 0);
-	Window *w = AllocateWindowDescFront(&_air_toolbar_desc, 0);
+	DeleteWindowByClass(WC_BUILD_TOOLBAR);
+	Window *w = AllocateWindowDescFront(&_air_toolbar_desc, TRANSPORT_AIR);
 	if (_patches.link_terraform_toolbar) ShowTerraformToolbar(w);
 }
 
diff --git a/src/dock_gui.cpp b/src/dock_gui.cpp
--- a/src/dock_gui.cpp
+++ b/src/dock_gui.cpp
@@ -232,8 +232,8 @@ void ShowBuildDocksToolbar()
 {
 	if (!IsValidPlayer(_current_player)) return;
 
-	DeleteWindowById(WC_BUILD_TOOLBAR, 0);
-	Window *w = AllocateWindowDesc(&_build_docks_toolbar_desc);
+	DeleteWindowByClass(WC_BUILD_TOOLBAR);
+	Window *w = AllocateWindowDescFront(&_build_docks_toolbar_desc, TRANSPORT_WATER);
 	if (_patches.link_terraform_toolbar) ShowTerraformToolbar(w);
 }
 
diff --git a/src/openttd.h b/src/openttd.h
--- a/src/openttd.h
+++ b/src/openttd.h
@@ -56,9 +56,10 @@ enum TransportType {
 	 * the values for road and rail.
 	 */
 	TRANSPORT_BEGIN = 0,
-	TRANSPORT_RAIL = 0,
-	TRANSPORT_ROAD = 1,
-	TRANSPORT_WATER, // = 2
+	TRANSPORT_RAIL = TRANSPORT_BEGIN,
+	TRANSPORT_ROAD,
+	TRANSPORT_WATER,
+	TRANSPORT_AIR,
 	TRANSPORT_END,
 	INVALID_TRANSPORT = 0xff,
 };
diff --git a/src/rail_gui.cpp b/src/rail_gui.cpp
--- a/src/rail_gui.cpp
+++ b/src/rail_gui.cpp
@@ -748,10 +748,10 @@ void ShowBuildRailToolbar(RailType railt
 	if (!ValParamRailtype(railtype)) return;
 
 	// don't recreate the window if we're clicking on a button and the window exists.
-	if (button < 0 || !(w = FindWindowById(WC_BUILD_TOOLBAR, 0)) || w->wndproc != BuildRailToolbWndProc) {
-		DeleteWindowById(WC_BUILD_TOOLBAR, 0);
+	if (button < 0 || !(w = FindWindowById(WC_BUILD_TOOLBAR, TRANSPORT_RAIL))) {
+		DeleteWindowByClass(WC_BUILD_TOOLBAR);
 		_cur_railtype = railtype;
-		w = AllocateWindowDesc(&_build_rail_desc);
+		w = AllocateWindowDescFront(&_build_rail_desc, TRANSPORT_RAIL);
 		SetupRailToolbar(railtype, w);
 	}
 
@@ -1597,8 +1597,8 @@ void ReinitGuiAfterToggleElrail(bool dis
 	if (disable && _last_built_railtype == RAILTYPE_ELECTRIC) {
 		Window *w;
 		_last_built_railtype = _cur_railtype = RAILTYPE_RAIL;
-		w = FindWindowById(WC_BUILD_TOOLBAR, 0);
-		if (w != NULL && w->wndproc == BuildRailToolbWndProc) {
+		w = FindWindowById(WC_BUILD_TOOLBAR, TRANSPORT_RAIL);
+		if (w != NULL) {
 			SetupRailToolbar(_cur_railtype, w);
 			SetWindowDirty(w);
 		}
@@ -1648,8 +1648,8 @@ static void SetDefaultRailGui()
 	}
 
 	_last_built_railtype = _cur_railtype = rt;
-	Window *w = FindWindowById(WC_BUILD_TOOLBAR, 0);
-	if (w != NULL && w->wndproc == BuildRailToolbWndProc) {
+	Window *w = FindWindowById(WC_BUILD_TOOLBAR, TRANSPORT_RAIL);
+	if (w != NULL) {
 		SetupRailToolbar(_cur_railtype, w);
 		SetWindowDirty(w);
 	}
diff --git a/src/road_gui.cpp b/src/road_gui.cpp
--- a/src/road_gui.cpp
+++ b/src/road_gui.cpp
@@ -682,8 +682,8 @@ void ShowBuildRoadToolbar(RoadType roadt
 	if (!IsValidPlayer(_current_player)) return;
 	_cur_roadtype = roadtype;
 
-	DeleteWindowById(WC_BUILD_TOOLBAR, 0);
-	Window *w = AllocateWindowDesc(roadtype == ROADTYPE_ROAD ? &_build_road_desc : &_build_tramway_desc);
+	DeleteWindowByClass(WC_BUILD_TOOLBAR);
+	Window *w = AllocateWindowDescFront(roadtype == ROADTYPE_ROAD ? &_build_road_desc : &_build_tramway_desc, TRANSPORT_ROAD);
 	if (_patches.link_terraform_toolbar) ShowTerraformToolbar(w);
 }