diff --git a/modem_manager.h b/modem_manager.h
index 1c926cb..be404f9 100644
--- a/modem_manager.h
+++ b/modem_manager.h
@@ -6,6 +6,7 @@
 #define SHILL_MODEM_MANAGER_
 
 #include <map>
+#include <string>
 #include <tr1/memory>
 
 #include <base/basictypes.h>