diff --git a/bookwyrm/models/user.py b/bookwyrm/models/user.py
index c9290e46..4cbe387f 100644
--- a/bookwyrm/models/user.py
+++ b/bookwyrm/models/user.py
@@ -1,4 +1,5 @@
 ''' database schema for user data '''
+import re
 from urllib.parse import urlparse
 
 from django.apps import apps
@@ -13,6 +14,7 @@ from bookwyrm.models.status import Status, Review
 from bookwyrm.settings import DOMAIN
 from bookwyrm.signatures import create_key_pair
 from bookwyrm.tasks import app
+from bookwyrm.utils import regex
 from .base_model import OrderedCollectionPageMixin
 from .base_model import ActivitypubMixin, BookWyrmModel
 from .federated_server import FederatedServer
@@ -168,15 +170,15 @@ class User(OrderedCollectionPageMixin, AbstractUser):
     def save(self, *args, **kwargs):
         ''' populate fields for new local users '''
         # this user already exists, no need to populate fields
-        if self.id:
-            return super().save(*args, **kwargs)
-
-        if not self.local:
+        if not self.local and not re.match(regex.full_username, self.username):
             # generate a username that uses the domain (webfinger format)
             actor_parts = urlparse(self.remote_id)
             self.username = '%s@%s' % (self.username, actor_parts.netloc)
             return super().save(*args, **kwargs)
 
+        if self.id or not self.local:
+            return super().save(*args, **kwargs)
+
         # populate fields for local users
         self.remote_id = 'https://%s/user/%s' % (DOMAIN, self.localname)
         self.inbox = '%s/inbox' % self.remote_id
diff --git a/bookwyrm/tests/models/test_fields.py b/bookwyrm/tests/models/test_fields.py
index 7935301e..e87855f6 100644
--- a/bookwyrm/tests/models/test_fields.py
+++ b/bookwyrm/tests/models/test_fields.py
@@ -111,6 +111,7 @@ class ActivitypubFields(TestCase):
         self.assertEqual(instance.max_length, 150)
         self.assertEqual(instance.unique, True)
         with self.assertRaises(ValidationError):
+            instance.run_validators('mouse')
             instance.run_validators('mouseexample.com')
             instance.run_validators('mouse@example.c')
             instance.run_validators('@example.com')
diff --git a/bookwyrm/tests/test_incoming.py b/bookwyrm/tests/test_incoming.py
index 980048bd..5d8bd110 100644
--- a/bookwyrm/tests/test_incoming.py
+++ b/bookwyrm/tests/test_incoming.py
@@ -487,6 +487,10 @@ class Incoming(TestCase):
 
     def test_handle_update_user(self):
         ''' update an existing user '''
+        # we only do this with remote users
+        self.local_user.local = False
+        self.local_user.save()
+
         datafile = pathlib.Path(__file__).parent.joinpath(
             'data/ap_user.json')
         userdata = json.loads(datafile.read_bytes())