diff --git a/src/Symfony/Bundle/FrameworkBundle/Tests/Translation/TranslatorTest.php b/src/Symfony/Bundle/FrameworkBundle/Tests/Translation/TranslatorTest.php
index 9f2012816a682..a93dd5e845144 100644
--- a/src/Symfony/Bundle/FrameworkBundle/Tests/Translation/TranslatorTest.php
+++ b/src/Symfony/Bundle/FrameworkBundle/Tests/Translation/TranslatorTest.php
@@ -92,6 +92,16 @@ public function testTransWithCaching()
         $this->assertEquals('foobarbax (sr@latin)', $translator->trans('foobarbax'));
     }
 
+    public function testTransWithCachingWithInvalidLocale()
+    {
+        $loader = $this->getMock('Symfony\Component\Translation\Loader\LoaderInterface');
+        $translator = $this->getTranslator($loader, array('cache_dir' => $this->tmpDir), '\Symfony\Bundle\FrameworkBundle\Tests\Translation\TranslatorWithInvalidLocale');
+        $translator->setLocale('invalid locale');
+
+        $this->setExpectedException('\InvalidArgumentException');
+        $translator->trans('foo');
+    }
+
     public function testGetLocale()
     {
         $request = $this->getMock('Symfony\Component\HttpFoundation\Request');
@@ -131,6 +141,49 @@ public function testGetLocale()
         $this->assertSame('en', $translator->getLocale());
     }
 
+    public function testGetLocaleWithInvalidLocale()
+    {
+        $request = $this->getMock('Symfony\Component\HttpFoundation\Request');
+
+        $request
+            ->expects($this->once())
+            ->method('getLocale')
+            ->will($this->returnValue('foo bar'))
+        ;
+        $request
+            ->expects($this->once())
+            ->method('getDefaultLocale')
+            ->will($this->returnValue('en-US'))
+        ;
+
+        $container = $this->getMock('Symfony\Component\DependencyInjection\ContainerInterface');
+
+        $container
+            ->expects($this->once())
+            ->method('isScopeActive')
+            ->with('request')
+            ->will($this->returnValue(true))
+        ;
+
+        $container
+            ->expects($this->once())
+            ->method('has')
+            ->with('request')
+            ->will($this->returnValue(true))
+        ;
+
+        $container
+            ->expects($this->any())
+            ->method('get')
+            ->with('request')
+            ->will($this->returnValue($request))
+        ;
+
+        $translator = new Translator($container, new MessageSelector());
+        $this->assertSame('en-US', $translator->getLocale());
+    }
+
+
     protected function getCatalogue($locale, $messages)
     {
         $catalogue = new MessageCatalogue($locale);
@@ -211,9 +264,9 @@ protected function getContainer($loader)
         return $container;
     }
 
-    public function getTranslator($loader, $options = array())
+    public function getTranslator($loader, $options = array(), $translatorClass = '\Symfony\Bundle\FrameworkBundle\Translation\Translator')
     {
-        $translator = new Translator(
+        $translator = new $translatorClass(
             $this->getContainer($loader),
             new MessageSelector(),
             array('loader' => array('loader')),
@@ -231,3 +284,14 @@ public function getTranslator($loader, $options = array())
         return $translator;
     }
 }
+
+class TranslatorWithInvalidLocale extends Translator
+{
+    /**
+     * {@inheritdoc}
+     */
+    public function setLocale($locale)
+    {
+        $this->locale = $locale;
+    }
+}
diff --git a/src/Symfony/Bundle/FrameworkBundle/Translation/Translator.php b/src/Symfony/Bundle/FrameworkBundle/Translation/Translator.php
index 0f99f6428e84e..92f90d4ff5c2b 100644
--- a/src/Symfony/Bundle/FrameworkBundle/Translation/Translator.php
+++ b/src/Symfony/Bundle/FrameworkBundle/Translation/Translator.php
@@ -68,7 +68,11 @@ public function __construct(ContainerInterface $container, MessageSelector $sele
     public function getLocale()
     {
         if (null === $this->locale && $this->container->isScopeActive('request') && $this->container->has('request')) {
-            $this->locale = $this->container->get('request')->getLocale();
+            try {
+                $this->setLocale($this->container->get('request')->getLocale());
+            } catch (\InvalidArgumentException $e) {
+                $this->setLocale($this->container->get('request')->getDefaultLocale());
+            }
         }
 
         return $this->locale;
@@ -89,6 +93,8 @@ protected function loadCatalogue($locale)
             return parent::loadCatalogue($locale);
         }
 
+        $this->assertValidLocale($locale);
+
         $cache = new ConfigCache($this->options['cache_dir'].'/catalogue.'.$locale.'.php', $this->options['debug']);
         if (!$cache->isFresh()) {
             $this->initialize();
diff --git a/src/Symfony/Component/HttpFoundation/Request.php b/src/Symfony/Component/HttpFoundation/Request.php
index f50219deae8cf..f180b3e6197f5 100644
--- a/src/Symfony/Component/HttpFoundation/Request.php
+++ b/src/Symfony/Component/HttpFoundation/Request.php
@@ -1358,6 +1358,16 @@ public function setDefaultLocale($locale)
         }
     }
 
+    /**
+     * Get the default locale.
+     *
+     * @return string
+     */
+    public function getDefaultLocale()
+    {
+        return $this->defaultLocale;
+    }
+
     /**
      * Sets the locale.
      *
diff --git a/src/Symfony/Component/Translation/Translator.php b/src/Symfony/Component/Translation/Translator.php
index 0ed30526d2b43..88178f8a83f17 100644
--- a/src/Symfony/Component/Translation/Translator.php
+++ b/src/Symfony/Component/Translation/Translator.php
@@ -306,7 +306,7 @@ protected function computeFallbackLocales($locale)
      *
      * @throws \InvalidArgumentException If the locale contains invalid characters
      */
-    private function assertValidLocale($locale)
+    protected function assertValidLocale($locale)
     {
         if (1 !== preg_match('/^[a-z0-9@_\\.\\-]*$/i', $locale)) {
             throw new \InvalidArgumentException(sprintf('Invalid "%s" locale.', $locale));