diff --git a/tarjan.h b/tarjan.h
index 1a80a95..53b0272 100644
--- a/tarjan.h
+++ b/tarjan.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_TARJAN_H__
-#define CHROMEOS_PLATFORM_UPDATE_ENGINE_TARJAN_H__
+#ifndef CHROMEOS_PLATFORM_UPDATE_ENGINE_TARJAN_H_
+#define CHROMEOS_PLATFORM_UPDATE_ENGINE_TARJAN_H_
 
 // This is an implemenation of Tarjan's algorithm which finds all
 // Strongly Connected Components in a graph.
@@ -36,4 +36,4 @@
 
 }  // namespace chromeos_update_engine
 
-#endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_TARJAN_H__
+#endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_TARJAN_H_