diff --git a/src/labthings_fastapi/outputs/blob.py b/src/labthings_fastapi/outputs/blob.py
index 75f73b8d..ac8f6d12 100644
--- a/src/labthings_fastapi/outputs/blob.py
+++ b/src/labthings_fastapi/outputs/blob.py
@@ -730,7 +730,7 @@ def attach_to_app(self, app: FastAPI) -> None:
 
 async def blob_serialisation_context_manager(
     request: Request,
-) -> AsyncGenerator[BlobDataManager]:
+) -> AsyncGenerator[BlobDataManager, None]:
     r"""Set context variables to allow blobs to be [de]serialised.
 
     In order to serialise a `.Blob` to a JSON-serialisable dictionary, we must
diff --git a/src/labthings_fastapi/server/__init__.py b/src/labthings_fastapi/server/__init__.py
index f20c0e28..b5816998 100644
--- a/src/labthings_fastapi/server/__init__.py
+++ b/src/labthings_fastapi/server/__init__.py
@@ -241,7 +241,7 @@ def _attach_things_to_server(self) -> None:
             thing.attach_to_server(self)
 
     @asynccontextmanager
-    async def lifespan(self, app: FastAPI) -> AsyncGenerator[None]:
+    async def lifespan(self, app: FastAPI) -> AsyncGenerator[None, None]:
         """Manage set up and tear down of the server and Things.
 
         This method is used as a lifespan function for the FastAPI app. See