diff --git a/library/Zend/Session/SessionManager.php b/library/Zend/Session/SessionManager.php
index 545befd3ce9..e013e0e7a94 100644
--- a/library/Zend/Session/SessionManager.php
+++ b/library/Zend/Session/SessionManager.php
@@ -332,7 +332,7 @@ public function isValid()
     {
         $validator = $this->getValidatorChain();
         $responses = $validator->triggerUntil('session.validate', $this, array($this), function ($test) {
-            return !$test;
+            return false === $test;
         });
         if ($responses->stopped()) {
             // If execution was halted, validation failed