``` [505] % z3 bug.smt2 unsat [506] % cvc4 -q --uf-ho bug.smt2 sat [507] % cat bug.smt2 (set-logic HORN) (declare-fun a (Bool) Bool) (declare-fun b (Bool) Bool) (assert (= a b)) (check-sat) [508] %``` ``` OS: Ubuntu 18.04 Commit: 5acf4b5