diff --git a/docs/workers.rst b/docs/workers.rst
index dd3a84ba0d..6ce7d88c11 100644
--- a/docs/workers.rst
+++ b/docs/workers.rst
@@ -223,6 +223,12 @@ following regular expressions::
     ^/_matrix/client/(api/v1|r0|unstable)/rooms/.*/members$
     ^/_matrix/client/(api/v1|r0|unstable)/rooms/.*/state$
 
+Additionally, the following REST endpoints can be handled, but all requests must
+be routed to the same instance::
+
+    ^/_matrix/client/(api/v1|r0|unstable)/register$
+
+
 ``synapse.app.user_dir``
 ~~~~~~~~~~~~~~~~~~~~~~~~
 
diff --git a/synapse/rest/client/v2_alpha/register.py b/synapse/rest/client/v2_alpha/register.py
index d78da50787..c52280c50c 100644
--- a/synapse/rest/client/v2_alpha/register.py
+++ b/synapse/rest/client/v2_alpha/register.py
@@ -665,7 +665,7 @@ class RegisterRestServlet(RestServlet):
                 device.
             is_guest (bool): Whether this is a guest account
         Returns:
-            defer.Deferred[(str, str)]: Tuple of device ID and access token
+            defer.Deferred[tuple[str, str]]: Tuple of device ID and access token
         """
         if self.hs.config.worker_app:
             r = yield self._register_device_client(