invalid variable expansion

[khimananda]

from radius -X log
I am using freeradius3.0.17

/etc/freeradius/mods-enabled/exec[36]: Failed parsing expanded string:
/etc/freeradius/mods-enabled/exec[36]: ...access-manager/artisan am:authorize %u
/etc/freeradius/mods-enabled/exec[36]: ^ Invalid variable expansion