diff --git a/ChangeLog b/ChangeLog
index 5f7f90d898..0662224a04 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Sat May 31 19:11:39 2008  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* enc/utf_16{be,le}.c (utf16{be,le}_code_to_mbc):
+	  fix codepoint to bytes.
+
 Sat May 31 18:28:17 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* suppress warnings with -Wwrite-string.
diff --git a/enc/utf_16be.c b/enc/utf_16be.c
index 2ef3199633..f80711d9bd 100644
--- a/enc/utf_16be.c
+++ b/enc/utf_16be.c
@@ -132,14 +132,12 @@ utf16be_code_to_mbc(OnigCodePoint code, UChar *buf,
   UChar* p = buf;
 
   if (code > 0xffff) {
-    unsigned int plane, high;
-
-    plane = code >> 16;
-    *p++ = (plane >> 2) + 0xd8;
-    high = (code & 0xff00) >> 8;
-    *p++ = ((plane & 0x03) << 6) + (high >> 2);
-    *p++ = (high & 0x02) + 0xdc;
-    *p   = (UChar )(code & 0xff);
+    unsigned int high = (code >> 10) + 0xD7C0;
+    unsigned int low = (code & 0x3FF) + 0xDC00;
+    *p++ = (high >> 8) & 0xFF;
+    *p++ = high & 0xFF;
+    *p++ = (low >> 8) & 0xFF;
+    *p++ = low & 0xFF;
     return 4;
   }
   else {
diff --git a/enc/utf_16le.c b/enc/utf_16le.c
index 33bfe08f47..c3712f4e18 100644
--- a/enc/utf_16le.c
+++ b/enc/utf_16le.c
@@ -126,15 +126,12 @@ utf16le_code_to_mbc(OnigCodePoint code, UChar *buf,
   UChar* p = buf;
 
   if (code > 0xffff) {
-    unsigned int plane, high;
-
-    plane = code >> 16;
-    high = (code & 0xff00) >> 8;
-
-    *p++ = ((plane & 0x03) << 6) + (high >> 2);
-    *p++ = (plane >> 2) + 0xd8;
-    *p++ = (UChar )(code & 0xff);
-    *p   = (high & 0x02) + 0xdc;
+    unsigned int high = (code >> 10) + 0xD7C0;
+    unsigned int low = (code & 0x3FF) + 0xDC00;
+    *p++ = high & 0xFF;
+    *p++ = (high >> 8) & 0xFF;
+    *p++ = low & 0xFF;
+    *p++ = (low >> 8) & 0xFF;
     return 4;
   }
   else {