diff --git a/src/Symfony/Bundle/TwigBundle/DependencyInjection/Configuration.php b/src/Symfony/Bundle/TwigBundle/DependencyInjection/Configuration.php
index 76faa0107e374..36b05857546de 100644
--- a/src/Symfony/Bundle/TwigBundle/DependencyInjection/Configuration.php
+++ b/src/Symfony/Bundle/TwigBundle/DependencyInjection/Configuration.php
@@ -147,7 +147,7 @@ private function addTwigOptions(ArrayNodeDefinition $rootNode)
                     ->normalizeKeys(false)
                     ->useAttributeAsKey('paths')
                     ->beforeNormalization()
-                        ->always()
+                        ->ifArray()
                         ->then(function ($paths) {
                             $normalized = [];
                             foreach ($paths as $path => $namespace) {
diff --git a/src/Symfony/Bundle/TwigBundle/Tests/DependencyInjection/ConfigurationTest.php b/src/Symfony/Bundle/TwigBundle/Tests/DependencyInjection/ConfigurationTest.php
index 41627c48041e3..6ed43087579ce 100644
--- a/src/Symfony/Bundle/TwigBundle/Tests/DependencyInjection/ConfigurationTest.php
+++ b/src/Symfony/Bundle/TwigBundle/Tests/DependencyInjection/ConfigurationTest.php
@@ -52,4 +52,16 @@ public function testArrayKeysInGlobalsAreNotNormalized()
 
         $this->assertSame(['global' => ['value' => ['some-key' => 'some-value']]], $config['globals']);
     }
+
+    public function testNullPathsAreConvertedToIterable()
+    {
+        $input = [
+            'paths' => null,
+        ];
+
+        $processor = new Processor();
+        $config = $processor->processConfiguration(new Configuration(), [$input]);
+
+        $this->assertSame([], $config['paths']);
+    }
 }