diff --git a/sru/onbsru.py b/sru/onbsru.py
index 8ec7bf5f17dd34c18fd1c18857f2f216bfb65097..377ef74e6aad0eea9c8bc7423d1786904038057e 100644
--- a/sru/onbsru.py
+++ b/sru/onbsru.py
@@ -23,7 +23,7 @@ class OnbRecordRetriever(almasru.RecordRetriever):
     def by_ac_num(self, ac_num: str):
         return self.by_marc_009(ac_num)
 
-    def get_pids(self, xml: Element) -> list:
+    def get_pids(self, xml) -> list:
         """
         Extract all PIDs from XML based on MARC 856 4 2.
         PIDs are identifiers migrated from a legacy system.