diff --git a/scim2_client/client.py b/scim2_client/client.py
index 10d1103..f4615f5 100644
--- a/scim2_client/client.py
+++ b/scim2_client/client.py
@@ -205,10 +205,13 @@ def get_resource_model(self, name: str) -> Optional[type[Resource]]:
     def _check_resource_model(
         self, resource_model: type[Resource], payload=None
     ) -> None:
-        if (
-            resource_model not in self.resource_models
-            and resource_model not in CONFIG_RESOURCES
-        ):
+        schema_to_check = resource_model.model_fields["schemas"].default[0]
+        for element in self.resource_models:
+            schema = element.model_fields["schemas"].default[0]
+            if schema_to_check == schema:
+                return
+
+        if resource_model not in CONFIG_RESOURCES:
             raise SCIMRequestError(
                 f"Unknown resource type: '{resource_model}'", source=payload
             )
@@ -640,13 +643,13 @@ def build_resource_models(
         for schema, resource_type in resource_types_by_schema.items():
             schema_obj = schema_objs_by_schema[schema]
             model = Resource.from_schema(schema_obj)
-            extensions = []
+            extensions: tuple[type[Extension], ...] = ()
             for ext_schema in resource_type.schema_extensions or []:
                 schema_obj = schema_objs_by_schema[ext_schema.schema_]
                 extension = Extension.from_schema(schema_obj)
-                extensions.append(extension)
+                extensions = extensions + (extension,)
             if extensions:
-                model = model[Union[tuple(extensions)]]
+                model = model[Union[extensions]]
             resource_models.append(model)
 
         return tuple(resource_models)
diff --git a/tests/test_delete.py b/tests/test_delete.py
index 4d17a22..6d6d4e2 100644
--- a/tests/test_delete.py
+++ b/tests/test_delete.py
@@ -1,12 +1,16 @@
 import pytest
 from scim2_models import Error
-from scim2_models import Group
+from scim2_models import Resource
 from scim2_models import User
 
 from scim2_client import RequestNetworkError
 from scim2_client import SCIMRequestError
 
 
+class UnregisteredResource(Resource):
+    schemas: list[str] = ["urn:test:schemas:UnregisteredResource"]
+
+
 def test_delete_user(httpserver, sync_client):
     """Nominal case for a User deletion."""
     httpserver.expect_request(
@@ -45,7 +49,7 @@ def test_errors(httpserver, code, sync_client):
 def test_invalid_resource_model(httpserver, sync_client):
     """Test that resource_models passed to the method must be part of SCIMClient.resource_models."""
     with pytest.raises(SCIMRequestError, match=r"Unknown resource type"):
-        sync_client.delete(Group(display_name="foobar"), id="foobar")
+        sync_client.delete(UnregisteredResource, id="foobar")
 
 
 def test_dont_check_response_payload(httpserver, sync_client):
diff --git a/tests/test_discovery.py b/tests/test_discovery.py
new file mode 100644
index 0000000..9006ac1
--- /dev/null
+++ b/tests/test_discovery.py
@@ -0,0 +1,96 @@
+import threading
+import wsgiref.simple_server
+from typing import Annotated
+from typing import Union
+
+import portpicker
+import pytest
+from httpx import Client
+from scim2_models import EnterpriseUser
+from scim2_models import Extension
+from scim2_models import Group
+from scim2_models import Meta
+from scim2_models import Required
+from scim2_models import ResourceType
+from scim2_models import User
+
+from scim2_client.engines.httpx import SyncSCIMClient
+
+scim2_server = pytest.importorskip("scim2_server")
+from scim2_server.backend import InMemoryBackend  # noqa: E402
+from scim2_server.provider import SCIMProvider  # noqa: E402
+
+
+class OtherExtension(Extension):
+    schemas: Annotated[list[str], Required.true] = [
+        "urn:ietf:params:scim:schemas:extension:Other:1.0:User"
+    ]
+
+    test: str | None = None
+    test2: list[str] | None = None
+
+
+def get_schemas():
+    schemas = [
+        User.to_schema(),
+        Group.to_schema(),
+        OtherExtension.to_schema(),
+        EnterpriseUser.to_schema(),
+    ]
+
+    # SCIMProvider register_schema requires meta object to be set
+    for schema in schemas:
+        schema.meta = Meta(resource_type="Schema")
+
+    return schemas
+
+
+def get_resource_types():
+    resource_types = [
+        ResourceType.from_resource(User[Union[EnterpriseUser, OtherExtension]]),
+        ResourceType.from_resource(Group),
+    ]
+
+    # SCIMProvider register_resource_type requires meta object to be set
+    for resource_type in resource_types:
+        resource_type.meta = Meta(resource_type="ResourceType")
+
+    return resource_types
+
+
+@pytest.fixture(scope="session")
+def server():
+    backend = InMemoryBackend()
+    provider = SCIMProvider(backend)
+    for schema in get_schemas():
+        provider.register_schema(schema)
+    for resource_type in get_resource_types():
+        provider.register_resource_type(resource_type)
+
+    host = "localhost"
+    port = portpicker.pick_unused_port()
+    httpd = wsgiref.simple_server.make_server(host, port, provider)
+
+    server_thread = threading.Thread(target=httpd.serve_forever)
+    server_thread.start()
+    try:
+        yield host, port
+    finally:
+        httpd.shutdown()
+        server_thread.join()
+
+
+def test_discovery_resource_types_multiple_extensions(server):
+    host, port = server
+    client = Client(base_url=f"http://{host}:{port}")
+    scim_client = SyncSCIMClient(client)
+
+    scim_client.discover()
+    assert scim_client.get_resource_model("User")
+    assert scim_client.get_resource_model("Group")
+
+    # Try to create a user to see if discover filled everything correctly
+    user_request = User[Union[EnterpriseUser, OtherExtension]](
+        user_name="bjensen@example.com"
+    )
+    scim_client.create(user_request)