diff --git a/include/mstch/mstch.hpp b/include/mstch/mstch.hpp
index 58d3330..20c4099 100644
--- a/include/mstch/mstch.hpp
+++ b/include/mstch/mstch.hpp
@@ -24,7 +24,7 @@ class object_t {
     return cache[name];
   }
 
-  bool has(const std::string name) const {
+  bool has(const std::string& name) const {
     return methods.count(name) != 0;
   }