diff --git a/sql/sql_acl.cc b/sql/sql_acl.cc
index fdd9b107bf2..090546e5013 100644
--- a/sql/sql_acl.cc
+++ b/sql/sql_acl.cc
@@ -3999,7 +3999,8 @@ bool mysql_grant(THD *thd, const char *db, List <LEX_USER> &list,
 
   if (lower_case_table_names && db)
   {
-    strmov(tmp_db,db);
+    strnmov(tmp_db,db,NAME_LEN);
+    tmp_db[NAME_LEN]= '\0';
     my_casedn_str(files_charset_info, tmp_db);
     db=tmp_db;
   }