diff --git a/photo-upload/app.py b/photo-upload/app.py
index 2649ec3..1545a43 100644
--- a/photo-upload/app.py
+++ b/photo-upload/app.py
@@ -189,7 +189,8 @@ def create_app(data_dir=None, token=None):
             if photos or len(archives) != 1:
                 abort(400, "Send either photos or one ZIP archive, not both")
             try:
-                with zipfile.ZipFile(archives[0].stream) as archive:
+                # Python 3.10's SpooledTemporaryFile lacks ZipFile's seekable API.
+                with zipfile.ZipFile(io.BytesIO(archives[0].read())) as archive:
                     members = [item for item in archive.infolist() if not item.is_dir()
                                and not item.filename.startswith("__MACOSX/")
                                and Path(item.filename).name != ".DS_Store"]