Authenticating usernames with spaces using MySQL

Hi I have an issue where I authenticate incoming DHCP requests on a broadband aggregation router using the Option 82 Port ID information as the username attribute within the RADIUS authentication request. Unfortunately the Port ID information includes spaces - and this is causing an issue where authentication fails using MySQL database, even though a username with spaces is configured in the MySQL database. If I use the /etc/raddb/users file it works OK, but I want to use MySQL accounting etc... Any ideas on how to work around this issue? Thanks Justin