Index: busybox-1.4.2/shell/ash.c
===================================================================
--- busybox-1.4.2.orig/shell/ash.c	2007-06-04 13:21:32.248074216 +0200
+++ busybox-1.4.2/shell/ash.c	2007-06-04 13:21:34.000807760 +0200
@@ -12237,9 +12237,18 @@
 	const char *p;
 	char **aptr;
 	int flag = argv[0][0] == 'r'? VREADONLY : VEXPORT;
+	int mask = ~0;
 	int notp;
 
-	notp = nextopt("p") - 'p';
+	while ((notp = nextopt("np"))) {
+		if (notp == 'n') {
+				mask = ~flag;
+		} else { /* p */
+			break;
+		}
+	}
+
+	notp -= 'p';
 	if (notp && ((name = *(aptr = argptr)))) {
 		do {
 			if ((p = strchr(name, '=')) != NULL) {
@@ -12247,10 +12256,11 @@
 			} else {
 				if ((vp = *findvar(hashvar(name), name))) {
 					vp->flags |= flag;
+					vp->flags &= mask;
 					continue;
 				}
 			}
-			setvar(name, p, flag);
+			setvar(name, p, flag & mask);
 		} while ((name = *++aptr) != NULL);
 	} else {
 		showvars(argv[0], flag, 0);