diff --git a/src/script/script_gui.cpp b/src/script/script_gui.cpp
--- a/src/script/script_gui.cpp
+++ b/src/script/script_gui.cpp
@@ -1229,7 +1229,7 @@ struct ScriptDebugWindow : public Window
 };
 
 /** Make a number of rows with buttons for each company for the Script debug window. */
-NWidgetBase *MakeCompanyButtonRowsScriptDebug()
+std::unique_ptr<NWidgetBase> MakeCompanyButtonRowsScriptDebug()
 {
 	return MakeCompanyButtonRows(WID_SCRD_COMPANY_BUTTON_START, WID_SCRD_COMPANY_BUTTON_END, COLOUR_GREY, 8, STR_AI_DEBUG_SELECT_AI_TOOLTIP);
 }