diff --git a/desktop/src-common/advent/screens/scene.clj b/desktop/src-common/advent/screens/scene.clj
index 10034c29..57a03a9a 100644
--- a/desktop/src-common/advent/screens/scene.clj
+++ b/desktop/src-common/advent/screens/scene.clj
@@ -544,7 +544,8 @@
 (defscreen scene
   :on-timer
   (fn [screen [entities]]
-    ((get-in entities [:room :timers (:id screen) 2]) screen entities))
+    (when-let [timer-fn (get-in entities [:room :timers (:id screen) 2])]
+      (timer-fn screen entities)))
 
   :on-show
   (fn [screen entities]