diff --git a/src/org/ntlab/deltaViewer/CollaborationLayout.java b/src/org/ntlab/deltaViewer/CollaborationLayout.java
index 0cc39a0..6b428c8 100644
--- a/src/org/ntlab/deltaViewer/CollaborationLayout.java
+++ b/src/org/ntlab/deltaViewer/CollaborationLayout.java
@@ -77,8 +77,17 @@
 		for (Alias a: aliasCollector.getAliasList()) {
 			int idx = -1;
 			if (a.getAliasType() == AliasType.FIELD) {
-				FieldAccess f = (FieldAccess) a.getOccurrencePoint().getStatement();
-				idx = references.indexOf(new Reference(f.getContainerObjId(), f.getValueObjId(), f.getContainerClassName(), f.getValueClassName()));
+				Reference ref = null;
+				if (a.getOccurrencePoint().getStatement() instanceof FieldAccess) {
+					FieldAccess f = (FieldAccess) a.getOccurrencePoint().getStatement();
+					ref = new Reference(f.getContainerObjId(), f.getValueObjId(), f.getContainerClassName(), f.getValueClassName());
+				} else if (a.getOccurrencePoint().getStatement() instanceof MethodInvocation) {
+					// A call to an enclosing instance.
+					MethodExecution m = a.getMethodExecution();
+					MethodInvocation i = (MethodInvocation) a.getOccurrencePoint().getStatement() ;
+					ref = new Reference(m.getThisObjId(), a.getObjectId(), m.getThisClassName(), i.getCalledMethodExecution().getArguments().get(0).getActualType());
+				}
+				idx = references.indexOf(ref);
 			} else if (a.getAliasType() == AliasType.ARRAY_ELEMENT) {
 				ArrayAccess aa = (ArrayAccess) a.getOccurrencePoint().getStatement();
 				idx = references.indexOf(new Reference(aa.getArrayObjectId(), aa.getValueObjectId(), aa.getArrayClassName(), aa.getValueClassName()));