Problem upgrading from drupal 6 to 7

I'm upgrading from drupal 6 to 7.
In Drupal 6 I was using the 6.x.1 branch.
During the update process (after the core upgrade, of course) I get this error:

Recoverable fatal error: Argument 2 passed to db_query() must be an array, string given, called in /sites/all/modules/ext/subdomain/subdomain.install on line 101 and defined in db_query() (line 2342 of /includes/database/database.inc

This line is exactly in the update 6200 function:

function subdomain_update_6200() {
  $ret = array();
   // ...
  $rows = _subdomain_fetch_rows(db_query("SELECT pid, src, dst FROM {url_alias} WHERE src LIKE '%s' AND dst LIKE '~%'", $pattern), strlen($pattern) - 1);
  // ....
}

Also tried with the dev version and the result was the same.
Any help would be appreciated.

Thanks.