--- loncom/interface/domainprefs.pm	2011/07/31 23:05:00	1.145
+++ loncom/interface/domainprefs.pm	2011/08/01 19:46:49	1.146
@@ -1,7 +1,7 @@
 # The LearningOnline Network with CAPA
 # Handler to set domain-wide configuration settings
 #
-# $Id: domainprefs.pm,v 1.145 2011/07/31 23:05:00 raeburn Exp $
+# $Id: domainprefs.pm,v 1.146 2011/08/01 19:46:49 raeburn Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -7099,7 +7099,12 @@ sub modify_usersessions {
                     }
                 }
             }
-            my @spares = sort(@okspares,$newspare);
+            my @spares;
+            if (($newspare ne '') && (!grep(/^\Q$newspare\E$/,@okspares))) {
+                @spares = sort(@okspares,$newspare);
+            } else {
+                @spares = sort(@okspares);
+            }
             $defaultshash{'usersessions'}{'spares'}{$lonhost}{$type} = \@spares;
         }
         if (keys(%spareschg) > 0) {