diff --git a/scl.py b/scl.py
index 5101962..2c511f6 100644
--- a/scl.py
+++ b/scl.py
@@ -247,7 +247,7 @@ def generate_post_map_image(
     with io.BytesIO() as map_image_file:
         map_image.save(map_image_file, format="WebP", method=6)
         map_media_post = mastodon_client.media_post(
-            map_image_file,
+            map_image_file.getvalue(),  # type: ignore
             mime_type="image/webp",
             description=alt_text,
         )