An lvar unified with a keyword behaves differently from a keyword

Question

(run 1 [q]
     (fresh [x]
            (== x :a)
            (== q ({:a 0} x))))
=> (nil)
(run 1 [q]
     (fresh [x]
            (== x :a)
            (== q ({:a 0} :a))))
=> (0)
(run 1 [q]
     (fresh [x]
            (== x :a)
            (== {:a 0} {x q})))
=> ()
(run 1 [q]
     (fresh [x]
            (== x :a)
            (== {:a 0} {:a q})))
=> (0)

Answer 1

Reference: https://clojure.atlassian.net/browse/LOGIC-182 (reported by alex+import)