diff --git a/zerver/lib/actions.py b/zerver/lib/actions.py
index 294aa81133..1d828f712c 100644
--- a/zerver/lib/actions.py
+++ b/zerver/lib/actions.py
@@ -2115,14 +2115,13 @@ def do_rename_stream(stream, new_name, log=True):
     # email forwarding address to display the correctly-escaped new name.
     return {"email_address": new_email}
 
-def do_change_stream_description(realm, stream_name, new_description):
-    # type: (Realm, Text, Text) -> None
-    stream = get_stream(stream_name, realm)
+def do_change_stream_description(stream, new_description):
+    # type: (Stream, Text) -> None
     stream.description = new_description
     stream.save(update_fields=['description'])
 
     event = dict(type='stream', op='update',
-                 property='description', name=stream_name,
+                 property='description', name=stream.name,
                  value=new_description)
     send_event(event, can_access_stream_user_ids(stream))
 
diff --git a/zerver/tests/test_events.py b/zerver/tests/test_events.py
index 613f16cfc4..cc072198de 100644
--- a/zerver/tests/test_events.py
+++ b/zerver/tests/test_events.py
@@ -1053,7 +1053,7 @@ class EventsRegisterTest(ZulipTestCase):
         error = add_schema_checker('events[1]', events[1])
         self.assert_on_error(error)
 
-        action = lambda: do_change_stream_description(get_realm('zulip'), 'test_stream', u'new description')
+        action = lambda: do_change_stream_description(stream, u'new description')
         events = self.do_test(action)
         error = stream_update_schema_checker('events[0]', events[0])
         self.assert_on_error(error)
diff --git a/zerver/views/streams.py b/zerver/views/streams.py
index 29aea0a9a6..2a942475ed 100644
--- a/zerver/views/streams.py
+++ b/zerver/views/streams.py
@@ -93,7 +93,7 @@ def update_stream_backend(request, user_profile, stream_id,
     (stream, recipient, sub) = access_stream_by_id(user_profile, stream_id)
 
     if description is not None:
-        do_change_stream_description(user_profile.realm, stream.name, description)
+        do_change_stream_description(stream, description)
     if new_name is not None:
         new_name = new_name.strip()
         # Will raise if the new name has invalid characters.