diff -up shadow-4.1.5.1/lib/commonio.c.backup-mode shadow-4.1.5.1/lib/commonio.c
--- shadow-4.1.5.1/lib/commonio.c.backup-mode	2012-05-18 21:44:54.000000000 +0200
+++ shadow-4.1.5.1/lib/commonio.c	2012-09-19 20:27:16.089444234 +0200
@@ -301,15 +301,12 @@ static int create_backup (const char *ba
 	struct utimbuf ub;
 	FILE *bkfp;
 	int c;
-	mode_t mask;
 
 	if (fstat (fileno (fp), &sb) != 0) {
 		return -1;
 	}
 
-	mask = umask (077);
-	bkfp = fopen (backup, "w");
-	(void) umask (mask);
+	bkfp = fopen_set_perms (backup, "w", &sb);
 	if (NULL == bkfp) {
 		return -1;
 	}