diff --git a/src/backups2datalad/asyncer.py b/src/backups2datalad/asyncer.py
index b613bfb..a7394fd 100644
--- a/src/backups2datalad/asyncer.py
+++ b/src/backups2datalad/asyncer.py
@@ -178,6 +178,7 @@ async def asset_loop(self, aia: AsyncIterator[RemoteAsset | None]) -> None:
                             )
                             downloading = False
                         else:
+                            assert isinstance(asset, RemoteZarrAsset)
                             self.nursery.start_soon(
                                 self.process_zarr,
                                 asset,