I'm running into this with some fdef specs in my tests. apparently there's some other problem that spec is endeavouring to explain?
https://clojure.atlassian.net/browse/CLJ-2481#icft=CLJ-2481
you can see in the comments this was closed as a dupe of https://clojure.atlassian.net/browse/CLJ-1975 which is still open
You can work around it by adding a :kind predicate to the s/coll-of