diff --git a/extent_ranges.h b/extent_ranges.h
index 2ab347a..c559849 100644
--- a/extent_ranges.h
+++ b/extent_ranges.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_EXTENT_RANGES_H__
-#define CHROMEOS_PLATFORM_UPDATE_ENGINE_EXTENT_RANGES_H__
+#ifndef CHROMEOS_PLATFORM_UPDATE_ENGINE_EXTENT_RANGES_H_
+#define CHROMEOS_PLATFORM_UPDATE_ENGINE_EXTENT_RANGES_H_
 
 #include <map>
 #include <set>
@@ -72,4 +72,4 @@
 
 }  // namespace chromeos_update_engine
 
-#endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_EXTENT_RANGES_H__
+#endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_EXTENT_RANGES_H_