diff --git a/node_external_ip_controller_async.py b/node_external_ip_controller_async.py
index 41f8d50..0109183 100644
--- a/node_external_ip_controller_async.py
+++ b/node_external_ip_controller_async.py
@@ -28,7 +28,6 @@ def is_valid_ip(ip):
 
 async def update_service_annotation(v1, service, external_ipset):
     try:
-        external_ips = list(external_ipset)
         service_name = service.metadata.name
         namespace = service.metadata.namespace
         logger.debug(f"Fetching service {service_name} in namespace {namespace}")
@@ -40,12 +39,13 @@ async def update_service_annotation(v1, service, external_ipset):
         logger.debug(f"Zlan Gateway IP: {zlan_gateway_ip}")
 
         if is_valid_ip(zlan_gateway_ip):
-            target_annotation = ",".join(external_ips) + "," + zlan_gateway_ip
+            external_ipset = set(external_ipset).add(zlan_gateway_ip)
         else:
-            target_annotation = ",".join(external_ips)
             logger.debug(
                 f"Invalid Zlan Gateway IP: {zlan_gateway_ip}, excluding from target annotation"
             )
+        external_ips = list(external_ipset)
+        target_annotation = ",".join(external_ips)
         if annotated_ipset != external_ipset:
             logger.debug(f"Current annotation: {current_annotation}: {annotated_ipset}")
             logger.debug(f"Target annotation: {target_annotation}: {external_ipset}")