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
@@ -641,7 +641,7 @@ struct AIDebugWindow : public Window {
 	{
 		/* Disable the companies who are not active or not an AI */
 		for (CompanyID i = COMPANY_FIRST; i < MAX_COMPANIES; i++) {
-			this->SetWidgetDisabledState(i + AID_WIDGET_COMPANY_BUTTON_START, !IsValidCompanyID(i) || !Company::Get(i)->is_ai);
+			this->SetWidgetDisabledState(i + AID_WIDGET_COMPANY_BUTTON_START, !Company::IsValidID(i) || !Company::Get(i)->is_ai);
 		}
 		this->DisableWidget(AID_WIDGET_RELOAD_TOGGLE);
 
@@ -659,7 +659,7 @@ struct AIDebugWindow : public Window {
 	virtual void OnPaint()
 	{
 		/* Check if the currently selected company is still active. */
-		if (ai_debug_company == INVALID_COMPANY || !IsValidCompanyID(ai_debug_company)) {
+		if (ai_debug_company == INVALID_COMPANY || !Company::IsValidID(ai_debug_company)) {
 			if (ai_debug_company != INVALID_COMPANY) {
 				/* Raise and disable the widget for the previous selection. */
 				this->RaiseWidget(ai_debug_company + AID_WIDGET_COMPANY_BUTTON_START);
@@ -669,7 +669,7 @@ struct AIDebugWindow : public Window {
 			}
 
 			for (CompanyID i = COMPANY_FIRST; i < MAX_COMPANIES; i++) {
-				if (IsValidCompanyID(i) && Company::Get(i)->is_ai) {
+				if (Company::IsValidID(i) && Company::Get(i)->is_ai) {
 					/* Lower the widget corresponding to this company. */
 					this->LowerWidget(i + AID_WIDGET_COMPANY_BUTTON_START);
 
@@ -690,7 +690,7 @@ struct AIDebugWindow : public Window {
 
 		/* Paint the company icons */
 		for (CompanyID i = COMPANY_FIRST; i < MAX_COMPANIES; i++) {
-			if (!IsValidCompanyID(i) || !Company::Get(i)->is_ai) {
+			if (!Company::IsValidID(i) || !Company::Get(i)->is_ai) {
 				/* Check if we have the company as an active company */
 				if (!this->IsWidgetDisabled(i + AID_WIDGET_COMPANY_BUTTON_START)) {
 					/* Bah, company gone :( */