diff --git a/src/tree_gui.cpp b/src/tree_gui.cpp
--- a/src/tree_gui.cpp
+++ b/src/tree_gui.cpp
@@ -96,7 +96,7 @@ public:
 		DrawSprite(tree_sprites[i].sprite, tree_sprites[i].pal, (r.left + r.right) / 2, r.bottom - 7);
 	}
 
-	virtual void OnClick(Point pt, int widget)
+	virtual void OnClick(Point pt, int widget, int click_count)
 	{
 		switch (widget) {
 			case BTW_TYPE_11: case BTW_TYPE_12: case BTW_TYPE_13: case BTW_TYPE_14: