diff --git a/src/org/ntlab/deltaViewer/CollaborationViewer.java b/src/org/ntlab/deltaViewer/CollaborationViewer.java
index 830674d..1db4730 100644
--- a/src/org/ntlab/deltaViewer/CollaborationViewer.java
+++ b/src/org/ntlab/deltaViewer/CollaborationViewer.java
@@ -386,6 +386,9 @@
 					}
 					if (!objectToVertexMap.containsKey(ref.getDstObjectId())) {
 						objectToVertexMap.put(ref.getDstObjectId(), new ObjectVertex(ref.getDstClassName(), null, 0, 0));
+					} else {
+						mxgraph.removeCells(new Object[] {objectToVertexMap.get(ref.getDstObjectId()).getCell()});
+						objectToVertexMap.get(ref.getDstObjectId()).setCell(null);
 					}
 				}
 			}