diff --git a/authentik/providers/scim/clients/groups.py b/authentik/providers/scim/clients/groups.py
index cf403d1f59..0a2f03caac 100644
--- a/authentik/providers/scim/clients/groups.py
+++ b/authentik/providers/scim/clients/groups.py
@@ -47,15 +47,16 @@ class SCIMGroupClient(SCIMClient[Group, SCIMProviderGroup, SCIMGroupSchema]):
 
     def to_schema(self, obj: Group, connection: SCIMProviderGroup) -> SCIMGroupSchema:
         """Convert authentik user into SCIM"""
-        raw_scim_group = super().to_schema(
-            obj,
-            connection,
-            schemas=(SCIM_GROUP_SCHEMA,),
-        )
+        raw_scim_group = super().to_schema(obj, connection)
         try:
             scim_group = SCIMGroupSchema.model_validate(delete_none_values(raw_scim_group))
         except ValidationError as exc:
             raise StopSync(exc, obj) from exc
+        if SCIM_GROUP_SCHEMA not in scim_group.schemas:
+            scim_group.schemas.insert(0, SCIM_GROUP_SCHEMA)
+        # As this might be unset, we need to tell pydantic it's set so ensure the schemas
+        # are included, even if its just the defaults
+        scim_group.schemas = list(scim_group.schemas)
         if not scim_group.externalId:
             scim_group.externalId = str(obj.pk)
 
diff --git a/authentik/providers/scim/clients/users.py b/authentik/providers/scim/clients/users.py
index 579d4c8381..2334f26ec1 100644
--- a/authentik/providers/scim/clients/users.py
+++ b/authentik/providers/scim/clients/users.py
@@ -31,15 +31,16 @@ class SCIMUserClient(SCIMClient[User, SCIMProviderUser, SCIMUserSchema]):
 
     def to_schema(self, obj: User, connection: SCIMProviderUser) -> SCIMUserSchema:
         """Convert authentik user into SCIM"""
-        raw_scim_user = super().to_schema(
-            obj,
-            connection,
-            schemas=(SCIM_USER_SCHEMA,),
-        )
+        raw_scim_user = super().to_schema(obj, connection)
         try:
             scim_user = SCIMUserSchema.model_validate(delete_none_values(raw_scim_user))
         except ValidationError as exc:
             raise StopSync(exc, obj) from exc
+        if SCIM_USER_SCHEMA not in scim_user.schemas:
+            scim_user.schemas.insert(0, SCIM_USER_SCHEMA)
+        # As this might be unset, we need to tell pydantic it's set so ensure the schemas
+        # are included, even if its just the defaults
+        scim_user.schemas = list(scim_user.schemas)
         if not scim_user.externalId:
             scim_user.externalId = str(obj.uid)
         return scim_user
diff --git a/authentik/providers/scim/tests/test_user.py b/authentik/providers/scim/tests/test_user.py
index 582ba03814..2f32b68857 100644
--- a/authentik/providers/scim/tests/test_user.py
+++ b/authentik/providers/scim/tests/test_user.py
@@ -91,6 +91,57 @@ class SCIMUserTests(TestCase):
             },
         )
 
+    @Mocker()
+    def test_user_create_custom_schema(self, mock: Mocker):
+        """Test user creation with custom schema"""
+        schema = SCIMMapping.objects.create(
+            name="custom_schema",
+            expression="""return {"schemas": ["foo"]}""",
+        )
+        self.provider.property_mappings.add(schema)
+        scim_id = generate_id()
+        mock.get(
+            "https://localhost/ServiceProviderConfig",
+            json={},
+        )
+        mock.post(
+            "https://localhost/Users",
+            json={
+                "id": scim_id,
+            },
+        )
+        uid = generate_id()
+        user = User.objects.create(
+            username=uid,
+            name=f"{uid} {uid}",
+            email=f"{uid}@goauthentik.io",
+        )
+        self.assertEqual(mock.call_count, 2)
+        self.assertEqual(mock.request_history[0].method, "GET")
+        self.assertEqual(mock.request_history[1].method, "POST")
+        self.assertJSONEqual(
+            mock.request_history[1].body,
+            {
+                "schemas": ["urn:ietf:params:scim:schemas:core:2.0:User", "foo"],
+                "active": True,
+                "emails": [
+                    {
+                        "primary": True,
+                        "type": "other",
+                        "value": f"{uid}@goauthentik.io",
+                    }
+                ],
+                "externalId": user.uid,
+                "name": {
+                    "familyName": uid,
+                    "formatted": f"{uid} {uid}",
+                    "givenName": uid,
+                },
+                "displayName": f"{uid} {uid}",
+                "userName": uid,
+            },
+        )
+
     @Mocker()
     def test_user_create_different_provider_same_id(self, mock: Mocker):
         """Test user creation with multiple providers that happen