Contact Checksum token not converted in text email format

When sending a CiviMail message and trying to allow non-logged in users to access a profile to update their information, the contact.checksum token does not work in the text format. It does work, however, in HTML format.

The link created in text format looks something like this: <site root>/sites/all/modules/civicrm/extern/url.php?u=33&qid=26 and when clicked it looks something like:
<site root>civicrm/profile/edit?reset=1&gid=1&id=3390&

{contact.checksum}

But in HTMl format the checksum token is converted perfectly and looks something like this:
<site root>/civicrm/profile/edit?reset=1&gid=1&id=3390&cs=4306090d027a3bdda4543879170712bc_1215622281_168

thanks