diff -Naur linux-2.4.26rc1/fs/open.c linux-2.4.26rc1_/fs/open.c
--- linux-2.4.26rc1/fs/open.c	2004-04-02 14:46:26.000000000 +0200
+++ linux-2.4.26rc1_/fs/open.c	2004-04-02 15:01:21.000000000 +0200
@@ -587,8 +587,10 @@
 	 * 19981026	David C Niemi <niemi@tux.org>
 	 *
 	 * Removed the fsuid check (see the comment above) -- 19990830 SD.
+	 *
+	 * Always remove SGID bit to comply with POSIX.
 	 */
-	if (((inode->i_mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) 
+	if (((inode->i_mode & S_ISGID) == S_ISGID) 
 		&& !S_ISDIR(inode->i_mode))
 	{
 		newattrs.ia_mode &= ~S_ISGID;