--- a/memory/build/mozjemalloc.h
+++ b/memory/build/mozjemalloc.h
@@ -1,14 +1,17 @@
 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+#ifndef mozjemalloc_h
+#define mozjemalloc_h
+
 #include "mozjemalloc_types.h"
 #include "mozilla/MacroArgs.h"
 
 /* Macro helpers */
 
 #define MACRO_CALL(a, b) a b
 /* Can't use macros recursively, so we need another one doing the same as above. */
 #define MACRO_CALL2(a, b) a b
@@ -67,8 +70,10 @@ struct DummyArenaAllocator {
   static return_type \
   moz_arena_ ## name(arena_id_t, ARGS_HELPER(TYPED_ARGS, ##__VA_ARGS__)) \
   { \
     return T::name(ARGS_HELPER(ARGS, ##__VA_ARGS__)); \
   }
 #define MALLOC_FUNCS MALLOC_FUNCS_MALLOC_BASE
 #include "malloc_decls.h"
 };
+
+#endif