--- loncom/auth/lonacc.pm	2014/10/18 21:40:06	1.159
+++ loncom/auth/lonacc.pm	2015/03/11 17:27:15	1.159.2.1
@@ -1,7 +1,7 @@
 # The LearningOnline Network
 # Cookie Based Access Handler
 #
-# $Id: lonacc.pm,v 1.159 2014/10/18 21:40:06 raeburn Exp $
+# $Id: lonacc.pm,v 1.159.2.1 2015/03/11 17:27:15 raeburn Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -290,7 +290,10 @@ sub sso_login {
 	return undef;
     }
 
-    my ($user) = ($r->user =~ m/([a-zA-Z0-9_\-@.]*)/);
+    my ($user) = ($r->user =~ m/^($match_username)$/);
+    if ($user eq '') {
+        return undef;
+    }
 
     my $query = $r->args;
     my %form;