--- a/tools/profiler/thread_helper.h
+++ b/tools/profiler/thread_helper.h
@@ -33,16 +33,19 @@
  * and other provisions required by the GPL or the LGPL. If you do not delete
  * the provisions above, a recipient may use your version of this file under
  * the terms of any one of the MPL, the GPL or the LGPL.
  *
  * ***** END LICENSE BLOCK ***** */
 
 // Cross-platform lightweight thread local data wrappers
 
+#ifndef MOZ_THREAD_HELPER_H
+#define MOZ_THREAD_HELPER_H
+
 #if defined(XP_WIN)
   // This file will get included in any file that wants to add
   // a profiler mark. In order to not bring <windows.h> together
   // we could include windef.h and winbase.h which are sufficient
   // to get the prototypes for the Tls* functions.
   // # include <windef.h>
   // # include <winbase.h>
   // Unfortunately, even including these headers causes
@@ -109,8 +112,9 @@ inline bool create(key* mykey) {
 }
 
 #endif
 
 }
 
 }
  
+#endif // MOZ_THREAD_HELPER_H
\ No newline at end of file