Clojurians Log v2

Hi luminous Clojurians! I have limited experience with luminus and fail to create a functioning WAR file with lein-uberwar (0.2.1) / Leiningen 2.9.1. and Clojure 1.10 and Java 8. WAR gets created but once deployed to Jetty or Tomcat I get HTTP Status 500: clojure.lang.ArityException: Wrong number of args (1) passed to: mytestapp.handler/app (from localhost:8080/mytestapp) (Notice, I didn't do any coding. It's a fresh luminus templated project with just a WAR option. (lein new luminus mytestapp +war) I get it perfectly running in dev mode using 'lein run'. Has anyone encountered this or has an idea? 1000 Thanks!!! First I posted at #clojure and they send me here.