diff --git a/usr.bin/su/su.1 b/usr.bin/su/su.1
index 26eb2c0d4ca2..d5aa8220d9fb 100644
--- a/usr.bin/su/su.1
+++ b/usr.bin/su/su.1
@@ -30,7 +30,7 @@
 .\" SUCH DAMAGE.
 .\"
 .\"	from: @(#)su.1	8.2 (Berkeley) 4/18/94
-.\"	$NetBSD: su.1,v 1.28 2003/02/25 10:35:56 wiz Exp $
+.\"	$NetBSD: su.1,v 1.29 2003/04/20 20:13:20 christos Exp $
 .\"
 .Dd January 19, 2003
 .Dt SU 1
@@ -106,6 +106,14 @@ If the invoked shell is
 this option prevents it from reading the
 .Dq Pa .cshrc
 file.
+If the invoked shell is
+.Xr sh 1 ,
+or 
+.Xr ksh 1 ,
+this option unsets
+.Ev ENV ,
+thus preventing the shell from executing the startup file pointed to by
+this variable.
 .It Fl l
 Simulate a full login.
 The environment is discarded except for
diff --git a/usr.bin/su/su.c b/usr.bin/su/su.c
index de549d333db0..c9481273dcfb 100644
--- a/usr.bin/su/su.c
+++ b/usr.bin/su/su.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: su.c,v 1.51 2002/11/16 15:59:31 itojun Exp $	*/
+/*	$NetBSD: su.c,v 1.52 2003/04/20 20:13:20 christos Exp $	*/
 
 /*
  * Copyright (c) 1988 The Regents of the University of California.
@@ -44,7 +44,7 @@ __COPYRIGHT(
 #if 0
 static char sccsid[] = "@(#)su.c	8.3 (Berkeley) 4/2/94";*/
 #else
-__RCSID("$NetBSD: su.c,v 1.51 2002/11/16 15:59:31 itojun Exp $");
+__RCSID("$NetBSD: su.c,v 1.52 2003/04/20 20:13:20 christos Exp $");
 #endif
 #endif /* not lint */
 
@@ -356,6 +356,8 @@ badlogin:
 			*np-- = "-f";
 		if (asme)
 			*np-- = "-m";
+	} else {
+		unsetenv("ENV");
 	}
 
 	if (asthem) {