diff --git a/include/mapnik/json/error_handler.hpp b/include/mapnik/json/error_handler.hpp
index f1a4f8b1e..7432c10f0 100644
--- a/include/mapnik/json/error_handler.hpp
+++ b/include/mapnik/json/error_handler.hpp
@@ -38,7 +38,10 @@ struct error_handler
         Iterator err_pos, boost::spirit::info const& what) const
     {
         std::stringstream s;
-        s << what << " expected but got: " << std::string(err_pos, std::min(err_pos + 16,last));
+        auto start = err_pos;
+        std::advance(err_pos,16);
+        auto end = err_pos;
+        s << what << " expected but got: " << std::string(start, end);
         throw std::runtime_error(s.str());
     }
 };