I think "pairmake" might not be quite right in master: https://github.com/FreeRADIUS/freeradius-server/blob/master/src/lib/valuepai... If "vp->operator" is T_OP_REG_{EQ,NE} then: 1. value is checked - if null, error 2. pairmake_xlat is called 3. this calls pairmake with value==NULL - goto 1, fail This causes problems with regexps in users files e.g. DEFAULT Attr =~ "some(.+)" ...which error out at startup with: Parse error (check) for entry blah: No regular expression found in ICzone