diff --git a/statefun-flink/statefun-flink-core/src/main/java/org/apache/flink/statefun/flink/core/httpfn/RetryingCallback.java b/statefun-flink/statefun-flink-core/src/main/java/org/apache/flink/statefun/flink/core/httpfn/RetryingCallback.java
index ffb7f7bb7..2f0289254 100644
--- a/statefun-flink/statefun-flink-core/src/main/java/org/apache/flink/statefun/flink/core/httpfn/RetryingCallback.java
+++ b/statefun-flink/statefun-flink-core/src/main/java/org/apache/flink/statefun/flink/core/httpfn/RetryingCallback.java
@@ -43,7 +43,7 @@ final class RetryingCallback implements Callback {
   private static final Duration INITIAL_BACKOFF_DURATION = Duration.ofMillis(10);
 
   private static final Set<Integer> RETRYABLE_HTTP_CODES =
-      new HashSet<>(Arrays.asList(409, 420, 408, 429, 499, 500));
+      new HashSet<>(Arrays.asList(400, 408, 409, 420, 429, 499, 500, 503, 504));
 
   private static final Logger LOG = LoggerFactory.getLogger(RetryingCallback.class);