diff --git a/ChangeLog b/ChangeLog
index 4f37eb9c60..f5c8ca8712 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed Jul 14 18:18:05 2010  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* regexec.c (match_at): add end point to enclen's argument.
+	  This only effect on compilinig with -DONIG_DEBUG_MATCH.
+
 Tue Jul 13 20:46:00 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* ext/dl/handle.c (rb_dlhandle_close): should not pass a dynamic
diff --git a/regexec.c b/regexec.c
index 13b6fadee2..c78d8ea998 100644
--- a/regexec.c
+++ b/regexec.c
@@ -1300,13 +1300,13 @@ match_at(regex_t* reg, const UChar* str, const UChar* end,
   s = (UChar* )sstart;
   while (1) {
 #ifdef ONIG_DEBUG_MATCH
-    {
+    if (s) {
       UChar *q, *bp, buf[50];
       int len;
       fprintf(stderr, "%4d> \"", (int )(s - str));
       bp = buf;
       for (i = 0, q = s; i < 7 && q < end; i++) {
-	len = enclen(encode, q);
+	len = enclen(encode, q, end);
 	while (len-- > 0) *bp++ = *q++;
       }
       if (q < end) { xmemcpy(bp, "...\"", 4); bp += 4; }