diff --git a/cpp/src/phonenumbers/utf/unicodetext.cc b/cpp/src/phonenumbers/utf/unicodetext.cc
index 11f68f762..1cde4baa6 100644
--- a/cpp/src/phonenumbers/utf/unicodetext.cc
+++ b/cpp/src/phonenumbers/utf/unicodetext.cc
@@ -27,6 +27,7 @@
 namespace i18n {
 namespace phonenumbers {
 
+using std::string;
 using std::stringstream;
 using std::max;
 using std::hex;