diff --git a/src/Symfony/Component/HttpFoundation/Session/Attribute/NamespacedAttributeBag.php b/src/Symfony/Component/HttpFoundation/Session/Attribute/NamespacedAttributeBag.php
index 138aa36145..25dcd22869 100644
--- a/src/Symfony/Component/HttpFoundation/Session/Attribute/NamespacedAttributeBag.php
+++ b/src/Symfony/Component/HttpFoundation/Session/Attribute/NamespacedAttributeBag.php
@@ -46,6 +46,10 @@ class NamespacedAttributeBag extends AttributeBag
         $attributes = $this->resolveAttributePath($name);
         $name = $this->resolveKey($name);
 
+        if (null === $attributes) {
+            return false;
+        }
+
         return array_key_exists($name, $attributes);
     }
 
@@ -57,6 +61,10 @@ class NamespacedAttributeBag extends AttributeBag
         $attributes = $this->resolveAttributePath($name);
         $name = $this->resolveKey($name);
 
+        if (null === $attributes) {
+            return $default;
+        }
+
         return array_key_exists($name, $attributes) ? $attributes[$name] : $default;
     }
 
@@ -120,12 +128,8 @@ class NamespacedAttributeBag extends AttributeBag
         unset($parts[count($parts)-1]);
 
         foreach ($parts as $part) {
-            if (!array_key_exists($part, $array)) {
-                if (!$writeContext) {
-                    return $array;
-                }
-
-                $array[$part] = array();
+            if (null !== $array && !array_key_exists($part, $array)) {
+                $array[$part] = $writeContext ? array() : null;
             }
 
             $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 432499e945..0f9ef0fb33 100644
--- a/src/Symfony/Component/HttpFoundation/Tests/Session/Attribute/NamespacedAttributeBagTest.php
+++ b/src/Symfony/Component/HttpFoundation/Tests/Session/Attribute/NamespacedAttributeBagTest.php
@@ -160,8 +160,10 @@ class NamespacedAttributeBagTest extends \PHPUnit_Framework_TestCase
             array('csrf.token/b', '4321', true),
             array('category', array('fishing' => array('first' => 'cod', 'second' => 'sole')), true),
             array('category/fishing', array('first' => 'cod', 'second' => 'sole'), true),
+            array('category/fishing/missing/first', null, false),
             array('category/fishing/first', 'cod', true),
             array('category/fishing/second', 'sole', true),
+            array('category/fishing/missing/second', null, false),
             array('user2.login', null, false),
             array('never', null, false),
             array('bye', null, false),