diff --git a/third_party/vaca/include/Vaca/String.h b/third_party/vaca/include/Vaca/String.h
index b1433d175..bbe54ae24 100644
--- a/third_party/vaca/include/Vaca/String.h
+++ b/third_party/vaca/include/Vaca/String.h
@@ -82,7 +82,10 @@ namespace Vaca {
     return convert_to<std::string, const Char*>(from);
   }
 
-  // Convert to String
+  // Convert to std::string
+  template<> VACA_DLL std::string convert_to(const int& from);
+
+  // Convert to std::wstring
   template<> VACA_DLL String convert_to(const std::string& from);
   template<> VACA_DLL String convert_to(const int& from);
   template<> VACA_DLL String convert_to(const long& from);
diff --git a/third_party/vaca/src/String.cpp b/third_party/vaca/src/String.cpp
index 0d496ad70..72b80d2d8 100644
--- a/third_party/vaca/src/String.cpp
+++ b/third_party/vaca/src/String.cpp
@@ -195,7 +195,12 @@ template<> double Vaca::convert_to(const String& from)
   return std::wcstod(from.c_str(), NULL);
 }
 
-template<> String Vaca::convert_to(const int& from)
+template<> std::string Vaca::convert_to(const int& from)
+{
+  return format_string("%d", from);
+}
+
+template<> std::wstring Vaca::convert_to(const int& from)
 {
   return format_string(L"%d", from);
 }