diff --git a/src/Symfony/Component/Translation/DataCollectorTranslator.php b/src/Symfony/Component/Translation/DataCollectorTranslator.php
index a94f9adabea6a..d1d5f4697bba3 100644
--- a/src/Symfony/Component/Translation/DataCollectorTranslator.php
+++ b/src/Symfony/Component/Translation/DataCollectorTranslator.php
@@ -116,16 +116,13 @@ public function getCollectedMessages()
      */
     private function collectMessage($locale, $domain, $id, $translation)
     {
-        if (null === $locale) {
-            $locale = $this->getLocale();
-        }
-
         if (null === $domain) {
             $domain = 'messages';
         }
 
         $id = (string) $id;
         $catalogue = $this->translator->getCatalogue($locale);
+        $locale = $catalogue->getLocale();
         if ($catalogue->defines($id, $domain)) {
             $state = self::MESSAGE_DEFINED;
         } elseif ($catalogue->has($id, $domain)) {
diff --git a/src/Symfony/Component/Translation/LoggingTranslator.php b/src/Symfony/Component/Translation/LoggingTranslator.php
index b46099c68f98a..8f5aec30616f5 100644
--- a/src/Symfony/Component/Translation/LoggingTranslator.php
+++ b/src/Symfony/Component/Translation/LoggingTranslator.php
@@ -109,10 +109,6 @@ public function __call($method, $args)
      */
     private function log($id, $domain, $locale)
     {
-        if (null === $locale) {
-            $locale = $this->getLocale();
-        }
-
         if (null === $domain) {
             $domain = 'messages';
         }
diff --git a/src/Symfony/Component/Translation/Translator.php b/src/Symfony/Component/Translation/Translator.php
index d62bfb68739cd..bb4134a64d030 100644
--- a/src/Symfony/Component/Translation/Translator.php
+++ b/src/Symfony/Component/Translation/Translator.php
@@ -222,21 +222,11 @@ public function getFallbackLocales()
      */
     public function trans($id, array $parameters = array(), $domain = null, $locale = null)
     {
-        if (null === $locale) {
-            $locale = $this->getLocale();
-        } else {
-            $this->assertValidLocale($locale);
-        }
-
         if (null === $domain) {
             $domain = 'messages';
         }
 
-        if (!isset($this->catalogues[$locale])) {
-            $this->loadCatalogue($locale);
-        }
-
-        return strtr($this->catalogues[$locale]->get((string) $id, $domain), $parameters);
+        return strtr($this->getCatalogue($locale)->get((string) $id, $domain), $parameters);
     }
 
     /**
@@ -246,23 +236,13 @@ public function trans($id, array $parameters = array(), $domain = null, $locale
      */
     public function transChoice($id, $number, array $parameters = array(), $domain = null, $locale = null)
     {
-        if (null === $locale) {
-            $locale = $this->getLocale();
-        } else {
-            $this->assertValidLocale($locale);
-        }
-
         if (null === $domain) {
             $domain = 'messages';
         }
 
-        if (!isset($this->catalogues[$locale])) {
-            $this->loadCatalogue($locale);
-        }
-
         $id = (string) $id;
-
-        $catalogue = $this->catalogues[$locale];
+        $catalogue = $this->getCatalogue($locale);
+        $locale = $catalogue->getLocale();
         while (!$catalogue->defines($id, $domain)) {
             if ($cat = $catalogue->getFallbackCatalogue()) {
                 $catalogue = $cat;
@@ -282,6 +262,8 @@ public function getCatalogue($locale = null)
     {
         if (null === $locale) {
             $locale = $this->getLocale();
+        } else {
+            $this->assertValidLocale($locale);
         }
 
         if (!isset($this->catalogues[$locale])) {
@@ -310,16 +292,8 @@ protected function getLoaders()
      */
     public function getMessages($locale = null)
     {
-        if (null === $locale) {
-            $locale = $this->getLocale();
-        }
-
-        if (!isset($this->catalogues[$locale])) {
-            $this->loadCatalogue($locale);
-        }
-
         $catalogues = array();
-        $catalogues[] = $catalogue = $this->catalogues[$locale];
+        $catalogues[] = $catalogue = $this->getCatalogue($locale);
         while ($catalogue = $catalogue->getFallbackCatalogue()) {
             $catalogues[] = $catalogue;
         }
diff --git a/src/Symfony/Component/Translation/TranslatorBagInterface.php b/src/Symfony/Component/Translation/TranslatorBagInterface.php
index e0312d9135576..6f650b5ee0f88 100644
--- a/src/Symfony/Component/Translation/TranslatorBagInterface.php
+++ b/src/Symfony/Component/Translation/TranslatorBagInterface.php
@@ -12,7 +12,7 @@
 namespace Symfony\Component\Translation;
 
 /**
- * TranslatorBagInterface
+ * TranslatorBagInterface.
  *
  * @author Abdellatif Ait boudad <a.aitboudad@gmail.com>
  */
@@ -23,6 +23,8 @@ interface TranslatorBagInterface
      *
      * @param string|null $locale The locale or null to use the default
      *
+     * @throws \InvalidArgumentException If the locale contains invalid characters
+     *
      * @return MessageCatalogueInterface
      */
     public function getCatalogue($locale = null);