diff --git a/src/interface/control_enum.hpp b/src/interface/control_enum.hpp
index 778a9389094..2110269fce8 100644
--- a/src/interface/control_enum.hpp
+++ b/src/interface/control_enum.hpp
@@ -40,7 +40,7 @@ class ControlEnum : public InterfaceControl
   void set_value(T value) { *m_value = value; }
   void bind_value(T* value) { m_value = value; }
 
-  void add_option(T key, std::string label) { m_options.push_back(std::make_pair(key, label)); }
+  void add_option(T key, const std::string& label) { m_options.push_back(std::make_pair(key, label)); }
 
   Rectf get_list_rect() const {
     return Rectf (