diff --git a/app/code/Magento/Security/Model/AdminSessionsManager.php b/app/code/Magento/Security/Model/AdminSessionsManager.php
index 154760eb835d1..605f99caddb1a 100644
--- a/app/code/Magento/Security/Model/AdminSessionsManager.php
+++ b/app/code/Magento/Security/Model/AdminSessionsManager.php
@@ -335,7 +335,11 @@ protected function createAdminSessionInfoCollection()
      */
     private function lastProlongIsOldEnough()
     {
-        $lastProlongTimestamp = strtotime($this->getCurrentSession()->getUpdatedAt());
+        $lastUpdatedTime = $this->getCurrentSession()->getUpdatedAt();
+        if($lastUpdatedTime === null || is_numeric($lastUpdatedTime)) {
+            $lastUpdatedTime = "now";
+        }
+        $lastProlongTimestamp = strtotime($lastUpdatedTime);
         $nowTimestamp = $this->authSession->getUpdatedAt();
 
         $diff = $nowTimestamp - $lastProlongTimestamp;