diff --git a/src/Symfony/Component/HttpFoundation/Session/Attribute/NamespacedAttributeBag.php b/src/Symfony/Component/HttpFoundation/Session/Attribute/NamespacedAttributeBag.php
index abbf37ee7c..f9df69e907 100644
--- a/src/Symfony/Component/HttpFoundation/Session/Attribute/NamespacedAttributeBag.php
+++ b/src/Symfony/Component/HttpFoundation/Session/Attribute/NamespacedAttributeBag.php
@@ -124,7 +124,13 @@ class NamespacedAttributeBag extends AttributeBag
 
         foreach ($parts as $part) {
             if (null !== $array && !array_key_exists($part, $array)) {
-                $array[$part] = $writeContext ? array() : null;
+                if (!$writeContext) {
+                    $null = null;
+
+                    return $null;
+                }
+
+                $array[$part] = array();
             }
 
             $array = &$array[$part];
diff --git a/src/Symfony/Component/HttpFoundation/Tests/Session/Attribute/NamespacedAttributeBagTest.php b/src/Symfony/Component/HttpFoundation/Tests/Session/Attribute/NamespacedAttributeBagTest.php
index f074ce1b26..ec4cd5ad1a 100644
--- a/src/Symfony/Component/HttpFoundation/Tests/Session/Attribute/NamespacedAttributeBagTest.php
+++ b/src/Symfony/Component/HttpFoundation/Tests/Session/Attribute/NamespacedAttributeBagTest.php
@@ -82,6 +82,17 @@ class NamespacedAttributeBagTest extends TestCase
         $this->assertEquals($exists, $this->bag->has($key));
     }
 
+    /**
+     * @dataProvider attributesProvider
+     */
+    public function testHasNoSideEffect($key, $value, $expected)
+    {
+        $expected = json_encode($this->bag->all());
+        $this->bag->has($key);
+
+        $this->assertEquals($expected, json_encode($this->bag->all()));
+    }
+
     /**
      * @dataProvider attributesProvider
      */
@@ -96,6 +107,17 @@ class NamespacedAttributeBagTest extends TestCase
         $this->assertEquals('default', $this->bag->get('user2.login', 'default'));
     }
 
+    /**
+     * @dataProvider attributesProvider
+     */
+    public function testGetNoSideEffect($key, $value, $expected)
+    {
+        $expected = json_encode($this->bag->all());
+        $this->bag->get($key);
+
+        $this->assertEquals($expected, json_encode($this->bag->all()));
+    }
+
     /**
      * @dataProvider attributesProvider
      */