diff --git a/nomad/groups.py b/nomad/groups.py
index b8d89b612f25a148f425a48f39c7925763dcb867..c964fcc560877c56d050eeee6b05d9b1b86c938a 100644
--- a/nomad/groups.py
+++ b/nomad/groups.py
@@ -39,7 +39,10 @@ class MongoUserGroup(Document):
     owner = StringField(required=True)
     members = ListField(StringField())
 
-    meta = {'indexes': ['group_name', 'owner', 'members']}
+    meta = {
+        'collection': 'user_group',
+        'indexes': ['group_name', 'owner', 'members'],
+    }
 
     @classmethod
     def q_by_ids(cls, group_ids: str | Iterable[str]) -> Q:
diff --git a/nomad/infrastructure.py b/nomad/infrastructure.py
index 02b35346c1dbdbd49b84b29080babad8d17f5c51..e5f458d0070e5408163b76f4aa2d5ee4856180bd 100644
--- a/nomad/infrastructure.py
+++ b/nomad/infrastructure.py
@@ -71,6 +71,7 @@ def setup():
     """
     setup_files()
     setup_mongo()
+    check_mongo()
     setup_elastic()
 
 
@@ -99,6 +100,25 @@ def setup_mongo(client=False):
     return mongo_client
 
 
+def check_mongo():
+    db = mongo_client.get_database(config.mongo.db_name)
+    names = db.list_collection_names()
+
+    expected_names = {'upload', 'user_group', 'entry', 'dataset', 'archive'}
+    if names != expected_names:
+        logger.warning(
+            f'Expected MongoDB collections: {expected_names} but found: {names}'
+        )
+
+    # regression https://gitlab.mpcdf.mpg.de/nomad-lab/nomad-FAIR/-/issues/2281
+    if 'mongo_user_group' in names:
+        logger.warning("""
+            The collection 'mongo_user_group' was found in MongoDB. It should be merged
+            into 'user_group'. This is a known issue. Please ask the NOMAD team
+            (support@nomad-lab.eu) if you need help with this.
+        """)
+
+
 def setup_elastic():
     """Creates connection to elastic search."""
     http_auth = None
diff --git a/tests/app/v1/routers/test_groups.py b/tests/app/v1/routers/test_groups.py
index a6476860391a51af092fa2e5624d06e0d4d0aac1..3b24ceea50396bbfc026f2a4c22d07c3dc5a2afc 100644
--- a/tests/app/v1/routers/test_groups.py
+++ b/tests/app/v1/routers/test_groups.py
@@ -1,8 +1,9 @@
 import pytest
-from .common import assert_response, perform_get, perform_post
+
 from nomad.app.v1.models.groups import UserGroup, UserGroupResponse
-from nomad.groups import get_user_group, user_group_exists
+from nomad.groups import MongoUserGroup, get_user_group, user_group_exists
 
+from .common import assert_response, perform_get, perform_post
 
 base_url = 'groups'
 
@@ -33,6 +34,10 @@ def assert_group(group, ref_group, keys=None):
         assert_unordered_lists(val, ref_val)
 
 
+def test_group_collection_name(groups_module):
+    MongoUserGroup._get_collection_name() == 'user_group'
+
+
 @pytest.mark.parametrize(
     'user_label, expected_status_code',
     [