&allow-other-keys not working

[hemml]

CL-USER> (defun xxx (a &key b &allow-other-keys) (format t "~A ~A~%" a b))
XXX
CL-USER> (xxx 1)
1 NIL
NIL
CL-USER> (xxx 1 :b 2)
1 2
NIL
CL-USER> (xxx 1 :b 2 :c 3)
ERROR: Unknown keyword argument C