diff --git a/include/mapnik/formatting/registry.hpp b/include/mapnik/formatting/registry.hpp
index 1c44e68dd..ef0f2c978 100644
--- a/include/mapnik/formatting/registry.hpp
+++ b/include/mapnik/formatting/registry.hpp
@@ -46,7 +46,7 @@ class registry : public singleton<registry, CreateStatic>,
 public:
     registry();
     ~registry() {}
-    void register_name(std::string name, from_xml_function_ptr ptr, bool overwrite=false);
+    void register_name(std::string const& name, from_xml_function_ptr ptr, bool overwrite=false);
     node_ptr from_xml(xml_node const& xml);
 private:
     std::map<std::string, from_xml_function_ptr> map_;
diff --git a/src/formatting/registry.cpp b/src/formatting/registry.cpp
index 527c81d71..0e2b8c81b 100644
--- a/src/formatting/registry.cpp
+++ b/src/formatting/registry.cpp
@@ -39,7 +39,7 @@ registry::registry()
     register_name("ExpressionFormat", &expression_format::from_xml);
 }
 
-void registry::register_name(std::string name, from_xml_function_ptr ptr, bool overwrite)
+void registry::register_name(std::string const& name, from_xml_function_ptr ptr, bool overwrite)
 {
     if (overwrite) {
         map_[name] = ptr;