diff --git a/conllusvg/UDPipe2UD.py b/conllusvg/UDPipe2UD.py
index ffb38711fe2d8c6a0e8c9395edb300e9076ceeb3..51da3b4fa156d0b4b2b58fc8d4777145fbbf6a1a 100755
--- a/conllusvg/UDPipe2UD.py
+++ b/conllusvg/UDPipe2UD.py
@@ -1,5 +1,5 @@
 #! /usr/bin/python -i
-# "UDPipe2UD.py" by Koichi Yasuoka, July 3, 2019.
+# "UDPipe2UD.py" by Koichi Yasuoka, September 15, 2019.
 
 class UDPipeEntry(object):
   def __init__(self,result):
@@ -9,10 +9,10 @@ class UDPipeEntry(object):
         w=UDPipeEntry(r)
         if w.id>0:
           t.append(w)
-      for i,w in enumerate(t):
-        w.head=w if w._head==0 else t[i+w._head-w.id]
-        w._parent=self
       self._tokens=t
+      for w in t:
+        w._parent=self
+        w.head=w._head
       self._result=result
     else:
       w=result.split("\t")
@@ -24,11 +24,11 @@ class UDPipeEntry(object):
       self._result=""
   def __setattr__(self,name,value):
     v=value
+    if name=="head":
+      t=self._parent._tokens
+      i=t.index(self)
+      v=self if v==0 else t[i+v-self.id]
     if hasattr(self,name):
-      if name=="head":
-        t=self._parent._tokens
-        i=t.index(self)
-        v=self if v==0 else t[i+v-self.id]
       if getattr(self,name)!=v:
         super(UDPipeEntry,self._parent).__setattr__("_result","")
         if name=="id":