diff --git a/psm_utils/io/pepxml.py b/psm_utils/io/pepxml.py
index da591ba..42e5b99 100644
--- a/psm_utils/io/pepxml.py
+++ b/psm_utils/io/pepxml.py
@@ -153,5 +153,5 @@ def _parse_psm(self, spectrum_query: dict, search_hit: dict) -> PSM:
                     for key in search_hit["search_score"]
                 }
             ),
-            rescoring_features=None,
+            rescoring_features=dict(),
         )