diff --git a/lib/SimpleSAML/Session.php b/lib/SimpleSAML/Session.php
index c215e36eacb01b8e8d8fa5074928c787788b2a4f..b13a64dfb99ec168ce7a942e2a90e6c4d2398783 100644
--- a/lib/SimpleSAML/Session.php
+++ b/lib/SimpleSAML/Session.php
@@ -57,7 +57,7 @@ class SimpleSAML_Session
      * This is used in the debug logs and error messages to easily track more information
      * about what went wrong.
      *
-     * @var int
+     * @var string|int
      */
     private $trackid = 0;