diff --git a/gpio_handler.h b/gpio_handler.h
index d1db7c2..580beb1 100644
--- a/gpio_handler.h
+++ b/gpio_handler.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_GPIO_HANDLER_H__
-#define CHROMEOS_PLATFORM_UPDATE_ENGINE_GPIO_HANDLER_H__
+#ifndef CHROMEOS_PLATFORM_UPDATE_ENGINE_GPIO_HANDLER_H_
+#define CHROMEOS_PLATFORM_UPDATE_ENGINE_GPIO_HANDLER_H_
 
 #include <libudev.h>
 
@@ -325,4 +325,4 @@
 
 }  // namespace chromeos_update_engine
 
-#endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_GPIO_HANDLER_H__
+#endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_GPIO_HANDLER_H_