diff --git a/src/Symfony/Component/HttpFoundation/Session/Storage/MockFileSessionStorage.php b/src/Symfony/Component/HttpFoundation/Session/Storage/MockFileSessionStorage.php
index 80aa44b06bc4e..2fd162b2c7cf2 100644
--- a/src/Symfony/Component/HttpFoundation/Session/Storage/MockFileSessionStorage.php
+++ b/src/Symfony/Component/HttpFoundation/Session/Storage/MockFileSessionStorage.php
@@ -97,6 +97,10 @@ public function regenerate($destroy = false, $lifetime = null)
      */
     public function save()
     {
+        if (!$this->started) {
+            return;
+        }
+
         file_put_contents($this->getFilePath(), serialize($this->data));
 
         // this is needed for Silex, where the session object is re-used across requests
diff --git a/src/Symfony/Component/HttpFoundation/Tests/Session/Storage/MockFileSessionStorageTest.php b/src/Symfony/Component/HttpFoundation/Tests/Session/Storage/MockFileSessionStorageTest.php
index f18089d92a822..8934156cc76f2 100644
--- a/src/Symfony/Component/HttpFoundation/Tests/Session/Storage/MockFileSessionStorageTest.php
+++ b/src/Symfony/Component/HttpFoundation/Tests/Session/Storage/MockFileSessionStorageTest.php
@@ -106,6 +106,23 @@ public function testMultipleInstances()
         $this->assertEquals('bar', $storage2->getBag('attributes')->get('foo'), 'values persist between instances');
     }
 
+    public function testSaveWithoutStart()
+    {
+        $storage1 = $this->getStorage();
+        $storage1->start();
+        $storage1->getBag('attributes')->set('foo', 'bar');
+        $storage1->save();
+
+        $storage2 = $this->getStorage();
+        $storage2->setId($storage1->getId());
+        $storage2->save();
+
+        $storage3 = $this->getStorage();
+        $storage3->setId($storage1->getId());
+        $storage3->start();
+        $this->assertEquals('bar', $storage3->getBag('attributes')->get('foo'), 'values persist between instances');
+    }
+
     private function getStorage()
     {
         $storage = new MockFileSessionStorage($this->sessionDir);