diff --git a/file_writer_mock.h b/file_writer_mock.h
index 004c3b1..02c8d97 100644
--- a/file_writer_mock.h
+++ b/file_writer_mock.h
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef CHROMEOS_PLATFORM_UPDATE_ENGINE_FILE_WRITER_MOCK_H__
-#define CHROMEOS_PLATFORM_UPDATE_ENGINE_FILE_WRITER_MOCK_H__
+#ifndef CHROMEOS_PLATFORM_UPDATE_ENGINE_FILE_WRITER_MOCK_H_
+#define CHROMEOS_PLATFORM_UPDATE_ENGINE_FILE_WRITER_MOCK_H_
 
 #include "gmock/gmock.h"
 #include "update_engine/file_writer.h"
@@ -19,4 +19,4 @@
 
 }  // namespace chromeos_update_engine
 
-#endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_FILE_WRITER_MOCK_H__
+#endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_FILE_WRITER_MOCK_H_