ignore the case insensitive in the users-file with using rlm_fastusers and EAP-TLS

hallo, I´d like to know, how can I adjust the freeradius configurations to ignore the case insensitive for all Identifiers existing into the file "/raddb/users" using rlm_fastusers with EAP-TLS. User-Names in the Access-Requests should namely mached with the Identifiers, which are configured in lower case. Thanks for your help Issam