diff --git a/shibboleth.php b/shibboleth.php
index c41e553..148a67f 100644
--- a/shibboleth.php
+++ b/shibboleth.php
@@ -376,7 +376,8 @@ function shibboleth_admin_hooks() {
 function shibboleth_session_active( $auto_login = false ) {
 	$active = false;
 	$method = shibboleth_getoption( 'shibboleth_attribute_access_method' );
-	$session = shibboleth_getenv( 'Shib-Session-ID' );
+	$shib_headers = shibboleth_getoption( 'shibboleth_headers', array(), true );
+	$session = shibboleth_getenv( $shib_headers['username']['name'] );
 
 	if ( $session && 'http' !== $method ) {
 		$active = true;