diff --git a/src/superannotate/lib/core/usecases/annotations.py b/src/superannotate/lib/core/usecases/annotations.py
index 83f4b6a15..2ea6623a0 100644
--- a/src/superannotate/lib/core/usecases/annotations.py
+++ b/src/superannotate/lib/core/usecases/annotations.py
@@ -707,6 +707,7 @@ def _upload_mask(self, item_data: ItemToUpload):
                     "annotation_bluemap_path"
                 ],
                 Body=item_data.mask,
+                ContentType="image/jpeg",
             )
 
     async def distribute_queues(self, items_to_upload: List[ItemToUpload]):