CQL substitution fail

(defn cat-and-subs [cat]
  (-> @(q/select categories
                 (q/where (and (not (= :super nil))
                               (= :super cat))))
      map-id
      (conj cat)))

(defn items-by-cat [cat]
  (-> items
      (q/select (q/where (p/in :category
                               (cat-and-subs cat))))))

@(items-by-cat 1) ; category 1 is not a super of anything - works fine

@(items-by-cat 3) ; 3 is the super of 5, this throws "The column index is out of range: 2, number of columns: 1."

(cat-and-subs 3) ; returns (3 5)

@(-> items
      (q/select (q/where (p/in :category [3 5])))) ; this works, and by substitution SHOULD be the same as (items-by-cat 3)