diff --git a/livekit-api/livekit/api/sip_service.py b/livekit-api/livekit/api/sip_service.py
index a7209284..d903efb0 100644
--- a/livekit-api/livekit/api/sip_service.py
+++ b/livekit-api/livekit/api/sip_service.py
@@ -330,10 +330,12 @@ async def update_sip_dispatch_rule_fields(
         Only provided fields will be updated.
         """
         update = SIPDispatchRuleUpdate(
-            name=name, metadata=metadata, rule=rule, attributes=attributes
+            name=name, 
+            metadata=metadata, 
+            rule=rule, 
+            attributes=attributes,
+            trunk_ids=ListUpdate(set=trunk_ids) if trunk_ids else None,
         )
-        if trunk_ids is not None:
-            update.trunk_ids = ListUpdate(set=trunk_ids)
         return await self._client.request(
             SVC,
             "UpdateSIPDispatchRule",