diff --git a/src/tree_gui.cpp b/src/tree_gui.cpp
--- a/src/tree_gui.cpp
+++ b/src/tree_gui.cpp
@@ -171,12 +171,12 @@ static const Widget _build_trees_widgets
 {    WIDGETS_END},
 };
 
-static const WindowDesc _build_trees_desc = {
+static const WindowDesc _build_trees_desc(
 	WDP_AUTO, WDP_AUTO, 143, 184, 143, 184,
 	WC_BUILD_TREES, WC_NONE,
 	WDF_STD_TOOLTIPS | WDF_STD_BTN | WDF_DEF_WIDGET | WDF_CONSTRUCTION,
-	_build_trees_widgets,
-};
+	_build_trees_widgets
+);
 
 void ShowBuildTreesToolbar()
 {