Index: src/org/eclipse/gmf/runtime/diagram/core/util/ViewRefactorHelper.java
===================================================================
RCS file: /cvsroot/modeling/org.eclipse.gmf/plugins/org.eclipse.gmf.runtime.diagram.core/src/org/eclipse/gmf/runtime/diagram/core/util/ViewRefactorHelper.java,v
retrieving revision 1.12
diff -u -r1.12 ViewRefactorHelper.java
--- src/org/eclipse/gmf/runtime/diagram/core/util/ViewRefactorHelper.java	25 Mar 2009 15:46:25 -0000	1.12
+++ src/org/eclipse/gmf/runtime/diagram/core/util/ViewRefactorHelper.java	26 Jun 2009 06:56:44 -0000
@@ -327,7 +327,17 @@
 				eClassMap.put(feature.getEContainingClass(), newStyle = newView.getStyle(feature.getEContainingClass()));
 			}
 			if (newStyle != null) {
-				newStyle.eSet(feature, oldStyle.eGet(feature));
+				if (!oldStyle.eIsSet(feature)) {
+					if (!newStyle.eIsSet(feature)) {
+						// both features are null; nothing to do
+						continue;
+					} else {
+						// new style's feature is set and must be cleared
+						newStyle.eUnset(feature);
+					}
+				} else {
+					newStyle.eSet(feature, oldStyle.eGet(feature));
+				}
 			}
 		}
 	}