diff --git a/pulsar-broker/src/main/java/org/apache/pulsar/broker/web/PulsarWebResource.java b/pulsar-broker/src/main/java/org/apache/pulsar/broker/web/PulsarWebResource.java
index 1183792729782..85605e201a07b 100644
--- a/pulsar-broker/src/main/java/org/apache/pulsar/broker/web/PulsarWebResource.java
+++ b/pulsar-broker/src/main/java/org/apache/pulsar/broker/web/PulsarWebResource.java
@@ -907,10 +907,11 @@ public static CompletableFuture<ClusterDataImpl> checkLocalOrGetPeerReplicationC
                 validationFuture.completeExceptionally(new RestException(Status.NOT_FOUND, "Namespace not found"));
             }
         }).exceptionally(ex -> {
+            Throwable cause = FutureUtil.unwrapCompletionException(ex);
             String msg = String.format("Failed to validate global cluster configuration : cluster=%s ns=%s  emsg=%s",
-                    localCluster, namespace, ex.getMessage());
+                    localCluster, namespace, cause.getMessage());
             log.error(msg);
-            validationFuture.completeExceptionally(new RestException(ex));
+            validationFuture.completeExceptionally(new RestException(cause));
             return null;
         });
         return validationFuture;