diff --git a/src/ifcopenshell-python/ifcopenshell/api/system/disconnect_port.py b/src/ifcopenshell-python/ifcopenshell/api/system/disconnect_port.py
index 1ff6609ce1..eddfae5f59 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/system/disconnect_port.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/system/disconnect_port.py
@@ -70,8 +70,8 @@ class Usecase:
         }
 
     def execute(self):
-        rels = self.settings["port"].ConnectedTo or []
-        rels += self.settings["port"].ConnectedFrom or []
+        rels = self.settings["port"].ConnectedTo or ()
+        rels += self.settings["port"].ConnectedFrom or ()
 
         for rel in rels:
             rel.RelatingPort.FlowDirection = None