diff --git a/src/Symfony/Component/HttpFoundation/Session/Storage/NativeSessionStorage.php b/src/Symfony/Component/HttpFoundation/Session/Storage/NativeSessionStorage.php
index 4f1c30ef52..4c5873728a 100644
--- a/src/Symfony/Component/HttpFoundation/Session/Storage/NativeSessionStorage.php
+++ b/src/Symfony/Component/HttpFoundation/Session/Storage/NativeSessionStorage.php
@@ -430,7 +430,7 @@ class NativeSessionStorage implements SessionStorageInterface
 
         foreach ($bags as $bag) {
             $key = $bag->getStorageKey();
-            $session[$key] = isset($session[$key]) ? $session[$key] : [];
+            $session[$key] = isset($session[$key]) && \is_array($session[$key]) ? $session[$key] : [];
             $bag->initialize($session[$key]);
         }