From chapter 5's pegthing.core https://www.braveclojure.com/functional-programming/ https://github.com/flyingmachine/pegthing/blob/c5d62f44a229964a0fa25b1fec0ceab2651fb436/src/pegthing/core.clj When I run this code in intellij-Cursive’s repl, I get the following error message: Syntax error macroexpanding clojure.core/ns at (core.clj:1:1). ((require [clojure.set :as set]) (:gen-class)) - failed: Extra input spec: :clojure.core.specs.alpha/ns-form Anyone know how to fix this?

Inside the ns declaration, you need :require (with the colon) and not just require

Thank you! @manutter51 That solved it.