diff --git a/ChangeLog b/ChangeLog
index 28c8c73f22..1238e5bec1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,7 +1,9 @@
-Sun Dec  9 03:29:02 2007  Tanaka Akira  <akr@fsij.org>
+Sun Dec  9 04:01:28 2007  Tanaka Akira  <akr@fsij.org>
 
 	* encoding.c (rb_enc_mbclen): return 1 if underlying implementation
 	  returns a length longer than e-p.
+	  (rb_enc_precise_mbclen): return needmore if underlying
+	  implementation returns a length longer than e-p.
 
 Sat Dec  8 17:59:40 2007  Tanaka Akira  <akr@fsij.org>
 
diff --git a/encoding.c b/encoding.c
index e902f6db0e..21b56f2636 100644
--- a/encoding.c
+++ b/encoding.c
@@ -496,9 +496,13 @@ rb_enc_mbclen(const char *p, const char *e, rb_encoding *enc)
 int
 rb_enc_precise_mbclen(const char *p, const char *e, rb_encoding *enc)
 {
+    int n;
     if (e <= p)
         return ONIGENC_CONSTRUCT_MBCLEN_NEEDMORE(1);
-    return ONIGENC_PRECISE_MBC_ENC_LEN(enc, (UChar*)p, (UChar*)e);
+    n = ONIGENC_PRECISE_MBC_ENC_LEN(enc, (UChar*)p, (UChar*)e);
+    if (e-p < n)
+        return ONIGENC_CONSTRUCT_MBCLEN_NEEDMORE(n-(e-p));
+    return n;
 }
 
 int rb_enc_get_ascii(const char *p, const char *e, rb_encoding *enc)