diff --git a/ChangeLog b/ChangeLog
index 0dcdf99ecc..ee3c4ab0d5 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Fri Nov 17 14:55:18 2000  WATANABE Hirofumi  <eban@ruby-lang.org>
+
+	* string.c (rb_str_succ): output should be NUL terminated.
+
 Fri Nov 17 02:54:15 2000  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* io.c (rb_io_close): need not to flush before closing.
diff --git a/string.c b/string.c
index 46f9725ce3..e068e44871 100644
--- a/string.c
+++ b/string.c
@@ -829,7 +829,7 @@ rb_str_succ(orig)
 	memmove(s+1, s, RSTRING(str)->len - n);
 	*s = c;
 	RSTRING(str)->len += 1;
-	
+	RSTRING(str)->ptr[RSTRING(str)->len] = '\0';
     }
 
     return str;