there were changes to the core data structures in order to support reducers, namely the addition of polymorphic reduction by the collection. See: https://githu

there were changes to the core data structures in order to support reducers, namely the addition of polymorphic reduction by the collection. See: https://github.com/clojure/clojure/commit/5b281880571573c5917781de932ce4789f18daec https://github.com/clojure/clojure/commit/5b281880571573c591... It was a pretty transparent change.