diff --git a/ast/buffer.go b/ast/buffer.go
index 93f4ff47a..4eac215b4 100644
--- a/ast/buffer.go
+++ b/ast/buffer.go
@@ -43,6 +43,21 @@ func (self *linkedNodes) Len() int {
     return self.size 
 }
 
+func (self *linkedNodes) Get(i int) (*Node) {
+    if self == nil {
+        return nil
+    }
+    if i >= 0 && i<self.size && i < _DEFAULT_NODE_CAP {
+        return &self.head[i]
+    } else if i >= _DEFAULT_NODE_CAP && i<self.size  {
+        a, b := i/_DEFAULT_NODE_CAP-1, i%_DEFAULT_NODE_CAP
+        if a < len(self.tail) {
+            return &self.tail[a][b]
+        }
+    }
+    return nil
+}
+
 func (self *linkedNodes) At(i int) (*Node) {
     if self == nil {
         return nil
diff --git a/ast/encode.go b/ast/encode.go
index 263ae5a9d..956809c2c 100644
--- a/ast/encode.go
+++ b/ast/encode.go
@@ -193,20 +193,9 @@ func (self *Node) encodeArray(buf *[]byte) error {
     
     *buf = append(*buf, '[')
 
-    var s = (*linkedNodes)(self.p)
     var started bool
-    if nb > 0 {
-        n := s.At(0)
-        if n.Exists() {
-            if err := n.encode(buf); err != nil {
-                return err
-            }
-            started = true
-        }
-    }
-
-    for i := 1; i < nb; i++ {
-        n := s.At(i)
+    for i := 0; i < nb; i++ {
+        n := self.nodeAt(i)
         if !n.Exists() {
             continue
         }
@@ -250,21 +239,10 @@ func (self *Node) encodeObject(buf *[]byte) error {
     
     *buf = append(*buf, '{')
 
-    var s = (*linkedPairs)(self.p)
     var started bool
-    if nb > 0 {
-        n := s.At(0)
-        if n.Value.Exists() {
-            if err := n.encode(buf); err != nil {
-                return err
-            }
-            started = true
-        }
-    }
-
-    for i := 1; i < nb; i++ {
-        n := s.At(i)
-        if !n.Value.Exists() {
+    for i := 0; i < nb; i++ {
+        n := self.pairAt(i)
+        if n == nil || !n.Value.Exists() {
             continue
         }
         if started {
diff --git a/ast/iterator.go b/ast/iterator.go
index a102c67be..64e1e5a90 100644
--- a/ast/iterator.go
+++ b/ast/iterator.go
@@ -122,7 +122,7 @@ next_start:
     } else {
         n := self.p.pairAt(self.i)
         self.i++
-        if !n.Value.Exists() {
+        if n == nil || !n.Value.Exists() {
             goto next_start
         }
         return n
diff --git a/ast/node.go b/ast/node.go
index 423b8ba81..7818ef4da 100644
--- a/ast/node.go
+++ b/ast/node.go
@@ -627,7 +627,7 @@ func (self *Node) UnsetByIndex(index int) (bool, error) {
     it := self.itype()
     if it == types.V_ARRAY {
         p = self.Index(index)
-    }else if it == types.V_OBJECT {
+    } else if it == types.V_OBJECT {
         if err := self.checkRaw(); err != nil {
             return false, err
         }
@@ -1174,6 +1174,19 @@ func (self *Node) nodeAt(i int) *Node {
         p = &stack.v
     } else {
         p = (*linkedNodes)(self.p)
+        if l := p.Len(); l != self.len() {
+            // some nodes got unset, iterate to skip them
+            for j:=0; j<l; j++ {
+                v := p.At(j)
+                if v.Exists() {
+                    i--
+                }
+                if i < 0 {
+                    return v
+                }
+            }
+            return nil
+        } 
     }
     return p.At(i)
 }
@@ -1185,6 +1198,19 @@ func (self *Node) pairAt(i int) *Pair {
         p = &stack.v
     } else {
         p = (*linkedPairs)(self.p)
+        if l := p.Len(); l != self.len() {
+            // some nodes got unset, iterate to skip them
+            for j:=0; j<l; j++ {
+                v := p.At(j)
+                if v != nil && v.Value.Exists() {
+                    i--
+                }
+                if i < 0 {
+                    return v
+                }
+            }
+           return nil
+       } 
     }
     return p.At(i)
 }
@@ -1336,8 +1362,8 @@ func (self *Node) removeNode(i int) {
         return
     }
     *node = Node{}
-    // NOTICE: for consistency with linkedNodes, we DOSEN'T reduce size here
-    // self.l--
+    // NOTICE: not be consistent with linkedNode.Len()
+    self.l--
 }
 
 func (self *Node) removePair(i int) {
@@ -1346,8 +1372,8 @@ func (self *Node) removePair(i int) {
         return
     }
     *last = Pair{}
-    // NOTICE: for consistency with linkedNodes, we DOSEN'T reduce size here
-    // self.l--
+    // NOTICE: should be consistent with linkedPair.Len()
+    self.l--
 }
 
 func (self *Node) toGenericArray() ([]interface{}, error) {
diff --git a/ast/node_test.go b/ast/node_test.go
index 8ab116692..c4624d71c 100644
--- a/ast/node_test.go
+++ b/ast/node_test.go
@@ -840,7 +840,7 @@ func TestUnset(t *testing.T) {
     hashtags := entities.Get("hashtags").Index(0)
     hashtags.Set("text2", newRawNode(`{}`, types.V_OBJECT))
     exist, err = hashtags.Unset("indices") // NOTICE: Unset() won't change node.Len() here
-    if !exist || err != nil || hashtags.len() != 3 {
+    if !exist || err != nil || hashtags.len() != 2 {
         t.Fatal(hashtags.len())
     }
     y, _ := hashtags.Get("text").String()