diff --git a/src/Symfony/Component/HttpFoundation/Session/Storage/MockArraySessionStorage.php b/src/Symfony/Component/HttpFoundation/Session/Storage/MockArraySessionStorage.php
index c26cc1334d..78404d7b44 100644
--- a/src/Symfony/Component/HttpFoundation/Session/Storage/MockArraySessionStorage.php
+++ b/src/Symfony/Component/HttpFoundation/Session/Storage/MockArraySessionStorage.php
@@ -60,7 +60,7 @@ class MockArraySessionStorage implements SessionStorageInterface
     /**
      * @var array
      */
-    protected $bags;
+    protected $bags = array();
 
     /**
      * Constructor.
diff --git a/src/Symfony/Component/HttpFoundation/Tests/Session/Storage/MockArraySessionStorageTest.php b/src/Symfony/Component/HttpFoundation/Tests/Session/Storage/MockArraySessionStorageTest.php
index 99da778b5f..82df5543eb 100644
--- a/src/Symfony/Component/HttpFoundation/Tests/Session/Storage/MockArraySessionStorageTest.php
+++ b/src/Symfony/Component/HttpFoundation/Tests/Session/Storage/MockArraySessionStorageTest.php
@@ -97,6 +97,30 @@ class MockArraySessionStorageTest extends TestCase
         $this->assertNotEquals('', $this->storage->getId());
     }
 
+    public function testClearClearsBags()
+    {
+        $this->storage->clear();
+
+        $this->assertSame(array(), $this->storage->getBag('attributes')->all());
+        $this->assertSame(array(), $this->storage->getBag('flashes')->peekAll());
+    }
+
+    public function testClearStartsSession()
+    {
+        $this->storage->clear();
+
+        $this->assertTrue($this->storage->isStarted());
+    }
+
+    public function testClearWithNoBagsStartsSession()
+    {
+        $storage = new MockArraySessionStorage();
+
+        $storage->clear();
+
+        $this->assertTrue($storage->isStarted());
+    }
+
     /**
      * @expectedException \RuntimeException
      */