diff --git a/dev/src/dev.clj b/dev/src/dev.clj
index 33f7b81960d1560feccb31f9a9b1638d6cbbec93..7b88025f06613ef764c85c478985d840994640dc 100644
--- a/dev/src/dev.clj
+++ b/dev/src/dev.clj
@@ -61,7 +61,7 @@
   []
   (server/start-web-server! #'handler/app)
   (when config/is-dev?
-    (malli-dev/start!))
+    (with-out-str (malli-dev/start!)))
   (when-not @initialized?
     (init!)))
 
diff --git a/src/metabase/util/malli.cljc b/src/metabase/util/malli.cljc
index 4af3d79318b3d31bce30e165dd760cd6c605fd3b..caab467e7aabbec1af9e56d98589ee8222806255 100644
--- a/src/metabase/util/malli.cljc
+++ b/src/metabase/util/malli.cljc
@@ -65,8 +65,8 @@
    (clojure.core/defn instrument!
      "Instrument a [[metabase.util.malli/defn]]."
      [id]
-     (minst/instrument! {:filters [(minst/-filter-var #(-> % meta :validate! (= id)))]
-                         :report  explain-fn-fail!}))
+     (with-out-str (minst/instrument! {:filters [(minst/-filter-var #(-> % meta :validate! (= id)))]
+                                       :report  explain-fn-fail!})))
    :cljs
    (clojure.core/defn instrument!
      "Instrument a [[metabase.util.malli/defn]]. No-op for ClojureScript. Instrumentation currently only works in