seq.indexof is producing incorrect values

[LeventErkok]

Fresh compile of z3 out of github.

(set-option :produce-models true)
(set-logic ALL)
(define-fun s0 () (Seq Int) (seq.++ (seq.unit 1) (seq.unit 2) (seq.unit 3)))
(define-fun s1 () (Seq Int) (seq.unit 2))
(declare-fun s2 () Int)
(assert (= s2 (seq.indexof s0 s1 0)))
(check-sat)
(get-value (s2))

z3 says:

sat
((s2 0))

Correct answer should be 1.

It appears that it correctly identifies non-occurences by assigning the value. -1, but for anything that's actually present, it simply returns 0.