diff --git a/Tests/Twig/GravatarExtensionTest.php b/Tests/Twig/GravatarExtensionTest.php
index 553fd48..3a1892f 100644
--- a/Tests/Twig/GravatarExtensionTest.php
+++ b/Tests/Twig/GravatarExtensionTest.php
@@ -2,10 +2,21 @@
 
 namespace Ornicar\GravatarBundle\Tests\Twig;
 
+use Ornicar\GravatarBundle\Templating\Helper\GravatarHelperInterface;
 use Ornicar\GravatarBundle\Twig\GravatarExtension;
 
 class GravatarExtensionTest extends \PHPUnit_Framework_TestCase
 {
+    /**
+     * @var GravatarHelperInterface
+     */
+    private $helper;
+
+    /**
+     * @var GravatarExtension
+     */
+    private $extension;
+
     public function setUp()
     {
         if (!class_exists('Twig_Extension')) {
@@ -34,13 +45,17 @@ public function testName()
 
     public function testFunctions()
     {
-        $this->assertContainsOnly('Twig_Function_Method', $this->extension->getFunctions());
+        $this->assertContainsOnlyInstancesOf('\Twig_SimpleFunction', $this->extension->getFunctions());
 
-        $this->assertEquals(array(
+        $expectedNames = array(
             'gravatar',
             'gravatar_hash',
             'gravatar_exists',
-        ), array_keys($this->extension->getFunctions()));
+        );
 
+        $functions = $this->extension->getFunctions();
+        foreach ($expectedNames as $n =>$expectedName) {
+            $this->assertSame($expectedName, $functions[$n]->getName());
+        }
     }
 }
diff --git a/Twig/GravatarExtension.php b/Twig/GravatarExtension.php
index 4c838b4..265260a 100644
--- a/Twig/GravatarExtension.php
+++ b/Twig/GravatarExtension.php
@@ -26,9 +26,9 @@ public function __construct(GravatarHelperInterface $helper)
     public function getFunctions()
     {
         return array(
-            'gravatar'        => new \Twig_Function_Method($this, 'getUrl'),
-            'gravatar_hash'   => new \Twig_Function_Method($this, 'getUrlForHash'),
-            'gravatar_exists' => new \Twig_Function_Method($this, 'exists'),
+            new \Twig_SimpleFunction('gravatar', array($this, 'getUrl')),
+            new \Twig_SimpleFunction('gravatar_hash', array($this, 'getUrlForHash')),
+            new \Twig_SimpleFunction('gravatar_exists', array($this, 'exists')),
         );
     }
 
diff --git a/composer.json b/composer.json
index 906f77a..765d20b 100644
--- a/composer.json
+++ b/composer.json
@@ -20,7 +20,10 @@
         "twig/extensions": "1.0.*"
     },
     "suggest" : {
-        "twig/twig" : ">=1.3.0"
+        "twig/twig" : "For gravatar twig extension usage"
+    },
+    "conflict": {
+        "twig/twig": "<1.12"
     },
     "autoload": {
         "psr-0": {