diff --git a/rocrate/model/file_or_dir.py b/rocrate/model/file_or_dir.py
index 8572e9b..4b37509 100644
--- a/rocrate/model/file_or_dir.py
+++ b/rocrate/model/file_or_dir.py
@@ -47,5 +47,5 @@ def __init__(self, crate, source=None, dest_path=None, fetch_remote=False,
             if is_url(str(source)):
                 identifier = os.path.basename(source) if fetch_remote else source
             else:
-                identifier = os.path.basename(str(source).rstrip(os.sep))
+                identifier = os.path.basename(str(source).rstrip("/"))
         super().__init__(crate, identifier, properties)