playing with modern-cljs: ClassCastException

[phi1ipp]

Hi, a newb here trying to follow modern-cljs, failed at step 15 (using 0.3.5-SNAPSHOT) and

(deftask testing
  "Add test/cljc for CLJ/CLJS testing purpose"
  []
  (set-env! :source-paths #(conj % "test/cljc"))
  identity)

(deftask tdd
  "Launch a TDD Environment"
  []
  (comp
   (serve :handler 'modern-cljs.core/app
          :resource-root "target"
          :reload true)
   (testing)
   (watch)
   (reload :ws-host "localhost")
   (cljs-repl)
   (test-cljs :out-file "main.js"
              :js-env :phantom
              :namespaces '#{modern-cljs.shopping.validators-test}
              :update-fs? true)
   (test :namespaces '#{modern-cljs.shopping.validators-test})
   (target :dir #{"target"})))

below is a stack-trace

Starting reload server on ws://localhost:49637
Writing boot_cljs_repl.cljs...
Adding: ([doo "0.1.8"]) to :dependencies
[boot-cljs] :out-file is deprecated, please use :ids
                              java.lang.Thread.run              Thread.java:  834
java.util.concurrent.ThreadPoolExecutor$Worker.run  ThreadPoolExecutor.java:  628
 java.util.concurrent.ThreadPoolExecutor.runWorker  ThreadPoolExecutor.java: 1128
               java.util.concurrent.FutureTask.run          FutureTask.java:  264
                                               ...                               
               clojure.core/binding-conveyor-fn/fn                 core.clj: 2030
                                 boot.core/boot/fn                 core.clj: 1033
                                               ...                               
                         boot.core/construct-tasks                 core.clj:  995
                                clojure.core/apply                 core.clj:  665
                                               ...                               
              boot.user$eval1475$fn__1476.doInvoke                         :   55
                                               ...                               
            crisptrutski.boot-cljs-test/eval625/fn       boot_cljs_test.clj:  298
                                clojure.core/swap!                 core.clj: 2345
java.lang.ClassCastException: class clojure.lang.Var$Unbound cannot be cast to class clojure.lang.IAtom (clojure.lang.Var$Unbound and clojure.lang.IAtom are in unnamed module of loader boot.AddableClassLoader @521e5a6a)
  clojure.lang.ExceptionInfo: class clojure.lang.Var$Unbound cannot be cast to class clojure.lang.IAtom (clojure.lang.Var$Unbound and clojure.lang.IAtom are in unnamed module of loader boot.AddableClassLoader @521e5a6a)
    line: 76

boot.properties

#http://boot-clj.com
#Sun Feb 17 11:27:01 CST 2019
BOOT_VERSION=2.8.2
BOOT_CLOJURE_VERSION=1.10.0
BOOT_CLOJURE_NAME=org.clojure/clojure

Any ideas what could go wrong?