diff --git a/src/main/java/com/hankcs/hanlp/dependency/common/Node.java b/src/main/java/com/hankcs/hanlp/dependency/common/Node.java
index 1b55cb168..fb93e035e 100644
--- a/src/main/java/com/hankcs/hanlp/dependency/common/Node.java
+++ b/src/main/java/com/hankcs/hanlp/dependency/common/Node.java
@@ -25,11 +25,9 @@
  */
 public class Node
 {
-    public final static Node NULL = new Node(new Term(CoNLLWord.NULL.NAME, Nature.n), -1);
     private final static Map<String, String> natureConverter = new TreeMap<String, String>();
     static
     {
-        NULL.label = "null";
         natureConverter.put("begin", "root");
         natureConverter.put("bg", "b");
         natureConverter.put("e", "y");
@@ -101,6 +99,11 @@ public class Node
         natureConverter.put("yg", "y");
         natureConverter.put("zg", "z");
     }
+    public final static Node NULL = new Node(new Term(CoNLLWord.NULL.NAME, Nature.n), -1);
+    static
+    {
+        NULL.label = "null";
+    }
     public String word;
     public String compiledWord;
     public String label;