diff --git a/src/server/game/AI/CreatureAIImpl.h b/src/server/game/AI/CreatureAIImpl.h
index 39261718180..30e239d0d11 100644
--- a/src/server/game/AI/CreatureAIImpl.h
+++ b/src/server/game/AI/CreatureAIImpl.h
@@ -19,6 +19,7 @@
 
 #include "Random.h"
 #include <type_traits>
+#include <functional>
 
 class WorldObject;