--- loncom/interface/loncommon.pm	2002/03/21 20:24:21	1.27
+++ loncom/interface/loncommon.pm	2002/03/23 14:54:16	1.28
@@ -1,7 +1,7 @@
 # The LearningOnline Network with CAPA
 # a pile of common routines
 #
-# $Id: loncommon.pm,v 1.27 2002/03/21 20:24:21 albertel Exp $
+# $Id: loncommon.pm,v 1.28 2002/03/23 14:54:16 albertel Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -392,7 +392,7 @@ sub no_cache {
 
 sub add_to_env {
   my ($name,$value)=@_;
-  if ($ENV{$name}) {
+  if (defined($ENV{$name})) {
     if (ref($ENV{$name})) {
       #already have multiple values
       push(@{ $ENV{$name} },$value);