diff --git a/src/Mod/BIM/ArchComponent.py b/src/Mod/BIM/ArchComponent.py
index ad04c2ce6a..836ff2c01b 100644
--- a/src/Mod/BIM/ArchComponent.py
+++ b/src/Mod/BIM/ArchComponent.py
@@ -782,7 +782,7 @@ class Component(ArchIFC.IfcProduct):
                     subvolume = o.getLinkedObject().Proxy.getSubVolume(o,host=obj)  # pass host obj (mostly Wall)
                 elif (Draft.getType(o) == "Roof") or (Draft.isClone(o,"Roof")):
                     # roofs define their own special subtraction volume
-                    subvolume = o.Proxy.getSubVolume(o)
+                    subvolume = o.Proxy.getSubVolume(o).copy()
                 elif hasattr(o,"Subvolume") and hasattr(o.Subvolume,"Shape"):
                     # Any other object with a Subvolume property
                     ## TODO - Part.Shape() instead?