diff --git a/src/day8/re_frame/trace/macros.clj b/src/day8/re_frame/trace/macros.clj
index b3b2542..c4a980a 100644
--- a/src/day8/re_frame/trace/macros.clj
+++ b/src/day8/re_frame/trace/macros.clj
@@ -5,3 +5,13 @@
   "Reads a file as a string. Slurp is wrapped in a macro so it can interact with local files before clojurescript compilation."
   [path]
   (slurp (io/resource path)))
+
+(defmacro with-cljs-devtools-prefs [prefs & body]
+  `(let [previous-config# (devtools.prefs/get-prefs)
+         prefs# ~prefs]
+     (try
+       (devtools.prefs/set-prefs! prefs#)
+       ~@body
+       (finally
+         (assert (= (devtools.prefs/get-prefs) prefs#) "someone modified devtools.prefs behind our back!")
+         (devtools.prefs/set-prefs! previous-config#)))))