diff --git a/jupyterhub/tests/test_user.py b/jupyterhub/tests/test_user.py
index 61e0270b..61723a85 100644
--- a/jupyterhub/tests/test_user.py
+++ b/jupyterhub/tests/test_user.py
@@ -29,12 +29,12 @@ async def test_userdict_get(db, attr):
         ["isin1", "isin2"],
         ["isin1"],
         ["notin", "isin1"],
-        ["new-group", "isin1"],
+        ["new-group", "new-group", "isin1"],
         [],
     ],
 )
 def test_sync_groups(app, user, group_names):
-    expected = sorted(group_names)
+    expected = sorted(set(group_names))
     db = app.db
     db.add(orm.Group(name="notin"))
     in_groups = [orm.Group(name="isin1"), orm.Group(name="isin2")]
diff --git a/jupyterhub/user.py b/jupyterhub/user.py
index 1a49f324..19e8011a 100644
--- a/jupyterhub/user.py
+++ b/jupyterhub/user.py
@@ -310,19 +310,19 @@ class User:
             return
 
         # log group changes
-        new_groups = set(group_names).difference(current_groups)
+        added_groups = new_groups.difference(current_groups)
         removed_groups = current_groups.difference(group_names)
-        if new_groups:
-            self.log.info(f"Adding user {self.name} to group(s): {new_groups}")
+        if added_groups:
+            self.log.info(f"Adding user {self.name} to group(s): {added_groups}")
         if removed_groups:
             self.log.info(f"Removing user {self.name} from group(s): {removed_groups}")
 
         if group_names:
             groups = (
-                self.db.query(orm.Group).filter(orm.Group.name.in_(group_names)).all()
+                self.db.query(orm.Group).filter(orm.Group.name.in_(new_groups)).all()
             )
             existing_groups = {g.name for g in groups}
-            for group_name in group_names:
+            for group_name in added_groups:
                 if group_name not in existing_groups:
                     # create groups that don't exist yet
                     self.log.info(
@@ -331,9 +331,9 @@ class User:
                     group = orm.Group(name=group_name)
                     self.db.add(group)
                     groups.append(group)
-            self.groups = groups
+            self.orm_user.groups = groups
         else:
-            self.groups = []
+            self.orm_user.groups = []
         self.db.commit()
 
     async def save_auth_state(self, auth_state):