diff --git a/src/ai/ai_gui.hpp b/src/ai/ai_gui.hpp
--- a/src/ai/ai_gui.hpp
+++ b/src/ai/ai_gui.hpp
@@ -18,7 +18,9 @@
 void ShowAIDebugWindow(CompanyID show_company = INVALID_COMPANY);
 void ShowAIConfigWindow();
 void ShowAIDebugWindowIfAIError();
+void InitializeAIGui();
 #else
+#include "../gui.h"
 #include "table/strings.h"
 
 static inline void ShowAIConfigWindow()
@@ -27,6 +29,7 @@ static inline void ShowAIConfigWindow()
 }
 static inline void ShowAIDebugWindow(CompanyID show_company = INVALID_COMPANY) {ShowAIConfigWindow();}
 static inline void ShowAIDebugWindowIfAIError() {}
+static inline void InitializeAIGui() {}
 #endif /* ENABLE_AI */
 
 #endif /* AI_GUI_HPP */