mysql expression failing

mysql_install_db: [ERROR] unknown variable 'pid-file=/run/mysqld/mysqld.pid'

configuration.nix:

      services.mysql = {
        enable = true;
        package = pkgs.mysql57;
        initialDatabases = [
          { name = "akron"; schema = ./akron.sql; }
        ];
        /*
        initialScript = ''
          GRANT ALL ON akron.* TO ${dbusername}@localhost
             IDENTIFIED BY '${dbpassword}';
        '';
        */
      };