diff --git a/avl/avl_test.go b/avl/avl_test.go
index b412a4d..06d92cd 100644
--- a/avl/avl_test.go
+++ b/avl/avl_test.go
@@ -42,11 +42,12 @@ func TestRotate(t *testing.T) {
 func TestIterator(t *testing.T) {
 	avl := New(utils.IntComparator)
 	for _, v := range []int{1, 2, 7, 4, 5, 6, 7, 14, 15, 20, 30, 21, 3} {
-		t.Error(v)
+		// t.Error(v)
 		avl.Put(v)
-		t.Error(avl.debugString())
+
 	}
 	t.Error(avl.TraversalDepth(1))
+	t.Error(avl.debugString())
 	iter := avl.Iterator()
 
 	for iter.Prev() {
diff --git a/avl/iterator.go b/avl/iterator.go
index a14347c..cf0230f 100644
--- a/avl/iterator.go
+++ b/avl/iterator.go
@@ -40,7 +40,7 @@ func (iter *Iterator) Next() (result bool) {
 	if iter.tstack.Size() == 0 {
 		if iter.up != nil {
 			iter.tstack.Push(iter.up)
-			iter.up = iter.getNextUp(iter.cur)
+			iter.up = iter.getNextUp(iter.up)
 		} else {
 			return false
 		}
@@ -62,7 +62,7 @@ func (iter *Iterator) getNextUp(cur *Node) *Node {
 		}
 		cur = cur.parent
 	}
-	return cur
+	return nil
 }
 
 func (iter *Iterator) curPushNextStack(cur *Node) {
@@ -84,7 +84,7 @@ func (iter *Iterator) getPrevUp(cur *Node) *Node {
 		}
 		cur = cur.parent
 	}
-	return cur
+	return nil
 }
 
 func (iter *Iterator) curPushPrevStack(cur *Node) {
@@ -116,7 +116,7 @@ func (iter *Iterator) Prev() (result bool) {
 	if iter.tstack.Size() == 0 {
 		if iter.up != nil {
 			iter.tstack.Push(iter.up)
-			iter.up = iter.getPrevUp(iter.cur)
+			iter.up = iter.getPrevUp(iter.up)
 		} else {
 			return false
 		}