diff --git a/action_unittest.cc b/action_unittest.cc
index 371f84d..8dd9edd 100644
--- a/action_unittest.cc
+++ b/action_unittest.cc
@@ -2,10 +2,13 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include <string>
 #include <gtest/gtest.h>
 #include "update_engine/action.h"
 #include "update_engine/action_processor.h"
 
+using std::string;
+
 namespace chromeos_update_engine {
 
 using chromeos_update_engine::ActionPipe;