diff --git a/requirements_dev_optional.txt b/requirements_dev_optional.txt
index 804bc6cf2c..f4f1c59e90 100644
--- a/requirements_dev_optional.txt
+++ b/requirements_dev_optional.txt
@@ -18,7 +18,5 @@ flake8==3.9.2
 pytest-cov==2.12.1
 pytest-doctestplus==0.10.1
 h5py==3.4.0
-s3fs==2021.6.0
-fsspec==2021.6.0
-aiobotocore!=1.4.0
+fsspec[s3]==2021.08.1
 moto[server]>=1.3.14
diff --git a/zarr/storage.py b/zarr/storage.py
index fc46f609ee..6ca6271dbf 100644
--- a/zarr/storage.py
+++ b/zarr/storage.py
@@ -1189,7 +1189,8 @@ def listdir(self, path=None):
                             for file_name in self.fs.find(entry_path):
                                 file_path = os.path.join(dir_path, file_name)
                                 rel_path = file_path.split(root_path)[1]
-                                new_children.append(rel_path.replace(os.path.sep, '.'))
+                                rel_path = rel_path.lstrip('/')
+                                new_children.append(rel_path.replace('/', '.'))
                         else:
                             new_children.append(entry)
                     return sorted(new_children)