diff --git a/changelog.d/9130.feature b/changelog.d/9130.feature
new file mode 100644
index 0000000000..4ec319f1f2
--- /dev/null
+++ b/changelog.d/9130.feature
@@ -0,0 +1 @@
+Add experimental support for handling and persistence of to-device messages to happen on worker processes.
diff --git a/synapse/handlers/devicemessage.py b/synapse/handlers/devicemessage.py
index fc974a82e8..0c7737e09d 100644
--- a/synapse/handlers/devicemessage.py
+++ b/synapse/handlers/devicemessage.py
@@ -163,7 +163,7 @@ class DeviceMessageHandler:
             await self.store.mark_remote_user_device_cache_as_stale(sender_user_id)
 
             # Immediately attempt a resync in the background
-            run_in_background(self._user_device_resync, sender_user_id)
+            run_in_background(self._user_device_resync, user_id=sender_user_id)
 
     async def send_device_message(
         self,