diff --git a/src/sort.cpp b/src/sort.cpp
index 3f13f9201..df71a1804 100644
--- a/src/sort.cpp
+++ b/src/sort.cpp
@@ -242,7 +242,7 @@ static bool sort_compare (int left, int right)
     // UDAs.
     else if ((column = Context::getContext ().columns[field]) != nullptr)
     {
-      std::string type = column->type ();
+      const std::string& type = column->type ();
       if (type == "numeric")
       {
         auto left_real  = strtof (((*global_data)[left].get_ref  (field)).c_str (), nullptr);