diff -ur php-4.3.3.orig/ext/mbstring/php_mbregex.c php-4.3.3/ext/mbstring/php_mbregex.c
--- php-4.3.3.orig/ext/mbstring/php_mbregex.c	Fri May  2 06:08:25 2003
+++ php-4.3.3/ext/mbstring/php_mbregex.c	Mon Sep 22 00:05:46 2003
@@ -557,7 +557,12 @@
 			}
 		} else { /* nomatch */
 			/* stick that last bit of string on our output */
-			_php_mb_regex_strbuf_ncat(&outdev, (const unsigned char *)&string[pos], string_len - pos);
+			int l = string_len - pos;
+			if (l > 0) {
+				_php_mb_regex_strbuf_ncat(&outdev, (const unsigned char *)&string[pos], l);
+			} else {
+				outdev.pos += l;
+			}
 		}
 	}