diff --git a/composer.json b/composer.json
index 47bb2de..7c42f41 100644
--- a/composer.json
+++ b/composer.json
@@ -14,7 +14,8 @@
         }
     ],
     "require": {
-        "php": ">=5.3.0"
+        "php": ">=5.3.0",
+        "symfony/intl": "~2.5"
     },
     "require-dev": {
         "phpspec/phpspec": "2.0.*",
diff --git a/phpspec.yml b/phpspec.yml
index 3a255e7..45b448b 100644
--- a/phpspec.yml
+++ b/phpspec.yml
@@ -1,2 +1,2 @@
 extensions:
-  - Coduo\PhpSpec\DataProviderExtension
+  - Coduo\PhpSpec\DataProvider\DataProviderExtension
diff --git a/src/Coduo/ToString/String.php b/src/Coduo/ToString/String.php
index f76e238..32e4084 100644
--- a/src/Coduo/ToString/String.php
+++ b/src/Coduo/ToString/String.php
@@ -67,7 +67,7 @@ private function castBooleanToString()
      */
     private function castDoubleToString()
     {
-        $formatter = new \NumberFormatter($this->locale, \NumberFormatter::PATTERN_DECIMAL);
+        $formatter = new \NumberFormatter($this->locale, \NumberFormatter::DEFAULT_STYLE);
         return $formatter->format($this->value);
     }
 }