diff --git a/src/tree_gui.cpp b/src/tree_gui.cpp
--- a/src/tree_gui.cpp
+++ b/src/tree_gui.cpp
@@ -84,7 +84,7 @@ public:
 		return size;
 	}
 
-	virtual void UpdateWidgetSize(int widget, Dimension *size, const Dimension &padding, Dimension *fill, Dimension *resize)
+	void UpdateWidgetSize(int widget, Dimension *size, const Dimension &padding, Dimension *fill, Dimension *resize) override
 	{
 		if (widget >= WID_BT_TYPE_11 && widget <= WID_BT_TYPE_34) {
 			Dimension d = GetMaxTreeSpriteSize();
@@ -102,7 +102,7 @@ public:
 		}
 	}
 
-	virtual void DrawWidget(const Rect &r, int widget) const
+	void DrawWidget(const Rect &r, int widget) const override
 	{
 		if (widget < WID_BT_TYPE_11 || widget > WID_BT_TYPE_34 || widget - WID_BT_TYPE_11 >= this->count) return;
 
@@ -111,7 +111,7 @@ public:
 		DrawSprite(tree_sprites[i].sprite, tree_sprites[i].pal, (r.left + r.right) / 2 + WD_FRAMERECT_LEFT, r.bottom - 7);
 	}
 
-	virtual void OnClick(Point pt, int widget, int click_count)
+	void OnClick(Point pt, int widget, int click_count) override
 	{
 		switch (widget) {
 			case WID_BT_TYPE_11: case WID_BT_TYPE_12: case WID_BT_TYPE_13: case WID_BT_TYPE_14:
@@ -138,17 +138,17 @@ public:
 		}
 	}
 
-	virtual void OnPlaceObject(Point pt, TileIndex tile)
+	void OnPlaceObject(Point pt, TileIndex tile) override
 	{
 		VpStartPlaceSizing(tile, VPM_X_AND_Y, DDSP_PLANT_TREES);
 	}
 
-	virtual void OnPlaceDrag(ViewportPlaceMethod select_method, ViewportDragDropSelectionProcess select_proc, Point pt)
+	void OnPlaceDrag(ViewportPlaceMethod select_method, ViewportDragDropSelectionProcess select_proc, Point pt) override
 	{
 		VpSelectTilesWithMethod(pt.x, pt.y, select_method);
 	}
 
-	virtual void OnPlaceMouseUp(ViewportPlaceMethod select_method, ViewportDragDropSelectionProcess select_proc, Point pt, TileIndex start_tile, TileIndex end_tile)
+	void OnPlaceMouseUp(ViewportPlaceMethod select_method, ViewportDragDropSelectionProcess select_proc, Point pt, TileIndex start_tile, TileIndex end_tile) override
 	{
 		if (pt.x != -1 && select_proc == DDSP_PLANT_TREES) {
 			DoCommandP(end_tile, this->tree_to_plant, start_tile,
@@ -159,13 +159,13 @@ public:
 	/**
 	 * Initialize the window data
 	 */
-	virtual void OnInit()
+	void OnInit() override
 	{
 		this->base  = _tree_base_by_landscape[_settings_game.game_creation.landscape];
 		this->count = _tree_count_by_landscape[_settings_game.game_creation.landscape];
 	}
 
-	virtual void OnPlaceObjectAbort()
+	void OnPlaceObjectAbort() override
 	{
 		this->RaiseButtons();
 	}