diff --git a/ext/mini_phone/mini_phone.cc b/ext/mini_phone/mini_phone.cc
index 5b95ba9..df55201 100644
--- a/ext/mini_phone/mini_phone.cc
+++ b/ext/mini_phone/mini_phone.cc
@@ -415,15 +415,15 @@ extern "C" VALUE rb_phone_number_area_code(VALUE self) {
   TypedData_Get_Struct(self, PhoneNumberInfo, &phone_number_info_type, phone_number_info);
 
   PhoneNumber *number = phone_number_info->phone_number;
-  string national_significant_number;
+  std::string national_significant_number;
   phone_util.GetNationalSignificantNumber(*number, &national_significant_number);
-  string area_code;
-  string subscriber_number;
+  std::string area_code;
+  std::string subscriber_number;
 
   int area_code_length = phone_util.GetLengthOfGeographicalAreaCode(*number);
   if (area_code_length > 0) {
     area_code = national_significant_number.substr(0, area_code_length);
-    subscriber_number = national_significant_number.substr(area_code_length, string::npos);
+    subscriber_number = national_significant_number.substr(area_code_length, std::string::npos);
   } else {
     area_code = "";
     subscriber_number = national_significant_number;
diff --git a/lib/mini_phone/version.rb b/lib/mini_phone/version.rb
index 3198857..e677f9a 100644
--- a/lib/mini_phone/version.rb
+++ b/lib/mini_phone/version.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module MiniPhone
-  VERSION = '1.1.9'
+  VERSION = '1.1.10'
 end