smt_compliant setting makes script unknown with a bizarre reason

[LeventErkok]

The attached script results in unknown. It prints:

unknown
(:reason-unknown "Sort mismatch at argument #2 for function (declare-fun = (Real Real) Bool) supplied sort is Int")

The unknown reason is truly confusing. There are no Real's in the benchmark, it's all about integers.

Surprisingly, if I comment out the very first line:

(set-option :smtlib2_compliant true)

then I get sat as the answer.

buggy.txt