diff --git a/src/play_clj/core.clj b/src/play_clj/core.clj
index 2d161f0..5d41774 100644
--- a/src/play_clj/core.clj
+++ b/src/play_clj/core.clj
@@ -504,8 +504,6 @@ keywords and functions in pairs."
 
     (set-screen! my-game main-screen text-screen)"
   [^Game game-object & screen-objects]
-  (assert (isa? (type game-object) Game) "The first argument in set-screen!
-must be the defgame object.")
   (let [run-fn! (fn [k & args]
                   (doseq [screen screen-objects]
                     (apply (get screen k) args)))]