diff --git a/core/ADTFactory.h b/core/ADTFactory.h
index 7700093d..ad25fc73 100644
--- a/core/ADTFactory.h
+++ b/core/ADTFactory.h
@@ -30,6 +30,9 @@
  * Version: $Id$
  */
 
+#ifndef _INCLUDE_SOURCEMOD_ADTFACTORY_H_
+#define _INCLUDE_SOURCEMOD_ADTFACTORY_H_
+
 #include <IADTFactory.h>
 #include "sm_globals.h"
 #include "sm_trie.h"
@@ -64,3 +67,5 @@ public: //IADTFactory
 	IBasicTrie *CreateBasicTrie();
 };
 
+#endif //_INCLUDE_SOURCEMOD_ADTFACTORY_H_
+