diff --git a/src/ifcopenshell-python/ifcopenshell/api/system/disconnect_port.py b/src/ifcopenshell-python/ifcopenshell/api/system/disconnect_port.py
index b6b72a192b..7ae790e753 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/system/disconnect_port.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/system/disconnect_port.py
@@ -65,6 +65,8 @@ def disconnect_port(file: ifcopenshell.file, port: ifcopenshell.entity_instance)
     rels += port.ConnectedFrom or ()
 
     for rel in rels:
+        rel.RelatingPort.FlowDirection = None
+        rel.RelatedPort.FlowDirection = None
         history = rel.OwnerHistory
         file.remove(rel)
         if history: