diff --git a/fs_storage/rooted_dir_file_system.py b/fs_storage/rooted_dir_file_system.py
index 91bae52200..0da5edd36f 100644
--- a/fs_storage/rooted_dir_file_system.py
+++ b/fs_storage/rooted_dir_file_system.py
@@ -27,7 +27,9 @@ def _join(self, path):
         # we need to normalize the path separator.
         path_posix = os.path.normpath(make_path_posix(path))
         root_posix = os.path.normpath(make_path_posix(self.path))
-        if not path_posix.startswith(root_posix):
+        if not root_posix.endswith("/"):
+            root_posix = root_posix + "/"
+        if path_posix != root_posix.rstrip("/") and not path_posix.startswith(root_posix):
             raise PermissionError(
                 f"Path {path} is not a subpath of the root path {self.path}"
             )