diff --git a/CHANGELOG.md b/CHANGELOG.md
index a946c9a1..5d4a0c8c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,7 @@ A preview of the next release can be installed from
 ## Unreleased
 
 - Bump babashka.http-client to v0.4.15
+- [#1619](https://github.com/babashka/babashka/issues/1619): Fix reflection issue with `Thread/sleep` in `core.async/timeout`
 
 ## 1.3.184 (2023-08-22)
 
diff --git a/src/babashka/impl/clojure/core/async.clj b/src/babashka/impl/clojure/core/async.clj
index 3c9cde05..a8f66ceb 100644
--- a/src/babashka/impl/clojure/core/async.clj
+++ b/src/babashka/impl/clojure/core/async.clj
@@ -6,6 +6,8 @@
             [sci.impl.copy-vars :refer [macrofy]]
             [sci.impl.vars :as vars]))
 
+(set! *warn-on-reflection* true)
+
 (def ^java.util.concurrent.Executor executor @#'async/thread-macro-executor)
 
 (def ^java.util.concurrent.Executor virtual-executor
@@ -72,7 +74,7 @@
   (if virtual-executor
     (let [chan (async/chan nil)]
       (.execute virtual-executor (fn []
-                                   (Thread/sleep ms)
+                                   (Thread/sleep (long ms))
                                    (async/close! chan)))
       chan)
     (async/timeout ms)))
diff --git a/test/babashka/async_test.clj b/test/babashka/async_test.clj
index 7fd1050c..770ac9aa 100644
--- a/test/babashka/async_test.clj
+++ b/test/babashka/async_test.clj
@@ -42,3 +42,11 @@
      [(async/go
         (async/<! (async/timeout 100))
         10)])))))")))))
+
+(deftest timeout-test
+  (is (nil? (edn/read-string (test-utils/bb nil "
+(first (async/<!!
+  (async/go
+    (async/alts!
+     [(async/go
+        (async/<! (async/timeout (int 100))))]))))")))))