diff --git a/src/org/ntlab/deltaExtractor/DeltaExtractor.java b/src/org/ntlab/deltaExtractor/DeltaExtractor.java
index d9b0f78..ac631ce 100644
--- a/src/org/ntlab/deltaExtractor/DeltaExtractor.java
+++ b/src/org/ntlab/deltaExtractor/DeltaExtractor.java
@@ -858,7 +858,7 @@
 
 	private ExtractedStructure extractSub(TracePoint creationTracePoint, Reference targetRef, IAliasCollector aliasCollector) {
 		eStructure = new ExtractedStructure();
-		eStructure.setRelatedTracePoint(creationTracePoint);
+		eStructure.setRelatedTracePoint(creationTracePoint.duplicate());
 		ArrayList<String> objList = new ArrayList<String>(); 
 		srcObject = targetRef.getSrcObject();
 		dstObject = targetRef.getDstObject();
@@ -917,7 +917,7 @@
 	 */
 	public ExtractedStructure extract(TracePoint thisTracePoint, ObjectReference anotherObj, IAliasCollector aliasCollector) {
 		eStructure = new ExtractedStructure();
-		eStructure.setRelatedTracePoint(thisTracePoint);
+		eStructure.setRelatedTracePoint(thisTracePoint.duplicate());
 		MethodExecution methodExecution = thisTracePoint.getMethodExecution();
 		if (!thisTracePoint.isMethodEntry()) {
 			thisTracePoint.stepNext();