diff --git a/sql/item_sum.cc b/sql/item_sum.cc
index 6ca3f024f61..1ee48dfb763 100644
--- a/sql/item_sum.cc
+++ b/sql/item_sum.cc
@@ -1986,6 +1986,7 @@ bool Item_func_group_concat::setup(THD *thd)
   }
   
   count_field_types(tmp_table_param,all_fields,0);
+  tmp_table_param->need_const= 1;
   if (table)
   {
     /*