diff --git a/sql/item_strfunc.cc b/sql/item_strfunc.cc
index 11c763ee173..094a0c56319 100644
--- a/sql/item_strfunc.cc
+++ b/sql/item_strfunc.cc
@@ -1570,7 +1570,7 @@ Item *Item_func_sysconst::safe_charset_converter(CHARSET_INFO *tocs)
     return NULL;
   }
   conv->str_value.copy();
-  conv->str_value.shrink_to_length();
+  conv->str_value.mark_as_const();
   return conv;
 }