diff --git a/src/ai/ai_gui.cpp b/src/ai/ai_gui.cpp
--- a/src/ai/ai_gui.cpp
+++ b/src/ai/ai_gui.cpp
@@ -236,7 +236,7 @@ static const WindowDesc _ai_list_desc(
 	WDP_CENTER, WDP_CENTER, 200, 234, 200, 234,
 	WC_AI_LIST, WC_NONE,
 	WDF_STD_TOOLTIPS | WDF_STD_BTN | WDF_DEF_WIDGET | WDF_UNCLICK_BUTTONS | WDF_RESIZABLE,
-	NULL, _nested_ai_list_widgets, lengthof(_nested_ai_list_widgets)
+	_nested_ai_list_widgets, lengthof(_nested_ai_list_widgets)
 );
 
 static void ShowAIListWindow(CompanyID slot)
@@ -435,7 +435,7 @@ static const WindowDesc _ai_settings_des
 	WDP_CENTER, WDP_CENTER, 200, 208, 500, 208,
 	WC_AI_SETTINGS, WC_NONE,
 	WDF_STD_TOOLTIPS | WDF_STD_BTN | WDF_DEF_WIDGET | WDF_UNCLICK_BUTTONS | WDF_RESIZABLE,
-	NULL, _nested_ai_settings_widgets, lengthof(_nested_ai_settings_widgets)
+	_nested_ai_settings_widgets, lengthof(_nested_ai_settings_widgets)
 );
 
 static void ShowAISettingsWindow(CompanyID slot)
@@ -484,7 +484,7 @@ static const WindowDesc _ai_config_desc(
 	WDP_CENTER, WDP_CENTER, 300, 172, 300, 172,
 	WC_GAME_OPTIONS, WC_NONE,
 	WDF_STD_TOOLTIPS | WDF_STD_BTN | WDF_DEF_WIDGET | WDF_UNCLICK_BUTTONS,
-	NULL, _nested_ai_config_widgets, lengthof(_nested_ai_config_widgets)
+	_nested_ai_config_widgets, lengthof(_nested_ai_config_widgets)
 );
 
 /**
@@ -952,7 +952,7 @@ static const WindowDesc _ai_debug_desc(
 	WDP_AUTO, WDP_AUTO, 299, 241, 299, 241,
 	WC_AI_DEBUG, WC_NONE,
 	WDF_STD_TOOLTIPS | WDF_STD_BTN | WDF_DEF_WIDGET | WDF_STICKY_BUTTON | WDF_RESIZABLE,
-	NULL, _nested_ai_debug_widgets, lengthof(_nested_ai_debug_widgets)
+	_nested_ai_debug_widgets, lengthof(_nested_ai_debug_widgets)
 );
 
 void ShowAIDebugWindow(CompanyID show_company)