diff --git a/lightly/api/serve.py b/lightly/api/serve.py
index 7dd1610df..08960efd3 100644
--- a/lightly/api/serve.py
+++ b/lightly/api/serve.py
@@ -10,7 +10,7 @@ def get_server(
     paths: Sequence[Path],
     host: str,
     port: int,
-):
+) -> ThreadingHTTPServer:
     """Returns an HTTP server that serves a local datasource.
 
     Args:
@@ -42,7 +42,7 @@ def do_OPTIONS(self) -> None:
             self.send_header("Access-Control-Allow-Methods", "GET, POST, OPTIONS")
             self.end_headers()
 
-        def send_response_only(self, code, message=None):
+        def send_response_only(self, code: int, message: str | None = None) -> None:
             super().send_response_only(code, message)
             self.send_header(
                 "Cache-Control", "no-store, must-revalidate, no-cache, max-age=-1"
diff --git a/pyproject.toml b/pyproject.toml
index 12363495f..405d16f07 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -223,7 +223,6 @@ exclude = '''(?x)(
     lightly/api/api_workflow_download_dataset.py |
     lightly/api/bitmask.py |
     lightly/api/_version_checking.py |
-    lightly/api/serve.py |
     lightly/api/patch.py |
     lightly/api/swagger_api_client.py |
     lightly/api/api_workflow_collaboration.py |