diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py

index 0016af44be..b6f400e9c3 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -376,8 +376,9 @@ class EventCreationHandler(object):
         self.notifier = hs.get_notifier()
         self.config = hs.config
         self.require_membership_for_aliases = hs.config.require_membership_for_aliases
-        self._events_shard_config = self.config.worker.events_shard_config
-        self._instance_name = hs.get_instance_name()
+        self._is_event_writer = (
+            self.config.worker.writers.events == hs.get_instance_name()
+        )
 
         self.room_invite_state_types = self.hs.config.room_invite_state_types
 
@@ -905,10 +906,9 @@ class EventCreationHandler(object):
 
         try:
             # If we're a worker we need to hit out to the master.
-            writer_instance = self._events_shard_config.get_instance(event.room_id)
-            if writer_instance != self._instance_name:
+            if not self._is_event_writer:
                 result = await self.send_event(
-                    instance_name=writer_instance,
+                    instance_name=self.config.worker.writers.events,
                     event_id=event.event_id,
                     store=self.store,
                     requester=requester,
@@ -976,9 +976,7 @@ class EventCreationHandler(object):
 
         This should only be run on the instance in charge of persisting events.
         """
-        assert self._events_shard_config.should_handle(
-            self._instance_name, event.room_id
-        )
+        assert self._is_event_writer
 
         if ratelimit:
             # We check if this is a room admin redacting an event so that we