http://cvsweb.php.net/viewvc.cgi/php-src/ext/mbstring/mbstring.c?r1=1.276&r2=1.277

--- ext/mbstring/mbstring.c	2006-05-11 16:47:34.000000000 +0200
+++ ext/mbstring/mbstring.c.oden	2009-03-05 10:29:05.000000000 +0100
@@ -1017,9 +1017,14 @@ PHP_RSHUTDOWN_FUNCTION(mbstring)
  	/*  clear overloaded function. */
 	if (MBSTRG(func_overload)){
 		p = &(mb_ovld[0]);
-		while (p->type > 0 && zend_hash_find(EG(function_table), p->save_func, strlen(p->save_func)+1 , (void **)&orig) == SUCCESS) {
-			zend_hash_update(EG(function_table), p->orig_func, strlen(p->orig_func)+1, orig, sizeof(zend_function), NULL);
-			zend_hash_del(EG(function_table), p->save_func, strlen(p->save_func)+1);
+		while (p->type > 0) {
+			if ((MBSTRG(func_overload) & p->type) == p->type && 
+				zend_hash_find(EG(function_table), p->save_func,
+							   strlen(p->save_func)+1, (void **)&orig) == SUCCESS) {
+				
+				zend_hash_update(EG(function_table), p->orig_func, strlen(p->orig_func)+1, orig, sizeof(zend_function), NULL);
+				zend_hash_del(EG(function_table), p->save_func, strlen(p->save_func)+1);
+			}
 			p++;
 		}
 	}