diff --git a/vcsserver/lib/archive_cache/backends/objectstore_cache.py b/vcsserver/lib/archive_cache/backends/objectstore_cache.py
--- a/vcsserver/lib/archive_cache/backends/objectstore_cache.py
+++ b/vcsserver/lib/archive_cache/backends/objectstore_cache.py
@@ -58,7 +58,7 @@ class S3Shard(BaseShard):
         # ensure folder in bucket exists
         destination = self.bucket
         if not self.fs.exists(destination):
-            self.fs.mkdir(destination, s3_additional_kwargs={})
+            self.fs.mkdir(destination)
 
         writer = self._get_writer(full_path, mode)