webform upgrade process does not handle table prefixing

After having installed and activated webform.module, I connected to the ADMINISTER => SETTINGS => WEBFORM menu. A clickable link prompted me to upgrade. When following this link, I get the following errors on screen:

Upgrading webform from -1 to 2004081900

user error: Table 'database.webform_submissions' doesn't exist
query: SELECT nid, sid, uid, UNIX_TIMESTAMP(created) as created, data FROM webform_submissions in /mydir/www/drupal/includes/database.mysql.inc on line 125.
Build -1

CREATE TABLE webform_submited_data ( nid int(10) unsigned not null, sid int(10) unsigned not null, name varchar(255) not null, data blob, PRIMARY KEY(nid, sid, name)) OK

Converting old submissions
Not implemented!

It looks like the names of the tables are hard coded. In my case, all tables are prefixed with 'drupal_' in the database, and this is correctly referencing in /includes/conf.php . webform.module does not check for this parameter here apparently.

As a sidenote, it is interesting that I was prompted to upgrade, as it was a fresh install. I would have thought that the content of webform.mysql was already up-to-date for this version. This problem may come from the value inserted in the variable table:

INSERT INTO drupal_variable VALUES ('webform_version', 'a:2:{s:4:"text";s:5:"1.1.0";s:5:"build";i:2004062100;}');

Is 2004062100 up to date ?

Anyway, after leaving this page and returning to ADMINISTER => SETTINGS => WEBFORM , the prompt to upgrade had disappeared.