diff --git a/include/mapnik/json/positions_grammar.hpp b/include/mapnik/json/positions_grammar.hpp
index a652e8f59..153542257 100644
--- a/include/mapnik/json/positions_grammar.hpp
+++ b/include/mapnik/json/positions_grammar.hpp
@@ -63,10 +63,10 @@ struct set_position_impl
 struct push_position_impl
 {
     using result_type = void;
-    template <typename T0,typename T1>
+    template <typename T0, typename T1>
     result_type operator() (T0 & coords, T1 const& pos) const
     {
-        if (pos) coords.push_back(*pos);
+        if (pos) coords.emplace_back(*pos);
     }
 };