diff --git a/lib/SimpleSAML/Session.php b/lib/SimpleSAML/Session.php
index 8d689f0f3aaa8f9b4cd281d110b1d27410000a5d..b93f8377c420564376c0cfc56a37a6909fa2275a 100644
--- a/lib/SimpleSAML/Session.php
+++ b/lib/SimpleSAML/Session.php
@@ -333,7 +333,8 @@ class SimpleSAML_Session implements SimpleSAML_ModifiedInfo {
 			(isset($authority) ? $authority : 'null'));
 		$this->authority = $authority;
 		$this->authenticated = $auth;
-		
+		$this->dirty = true;
+
 		if ($auth) {	
 			$this->clearNeedAuthFlag();
 			$this->sessionstarted = time();