multiplex broken with sort-by

[den1k]

;; this works
(sequence
  (comp (x/by-key :foo (x/into []))
        (x/sort-by first))
  [{:foo 2} {:foo 1} {:foo 1}])
=> ([1 [{:foo 1} {:foo 1}]] [2 [{:foo 2}]])

;; this breaks
(sequence
  (comp (x/by-key :foo (x/into []))
        (x/multiplex [(x/sort-by first)]))
  [{:foo 2} {:foo 1} {:foo 1}])
Execution error (ArityException) at net.cgrand.xforms/multiplex$fn$reify$fn (xforms.cljc:710).
Wrong number of args (3) passed to: net.cgrand.xforms/sort/fn--25064/fn--25065