diff --git a/src/Symfony/Component/DependencyInjection/Compiler/AutowirePass.php b/src/Symfony/Component/DependencyInjection/Compiler/AutowirePass.php
index 3b85543b8b956..c29953775574f 100644
--- a/src/Symfony/Component/DependencyInjection/Compiler/AutowirePass.php
+++ b/src/Symfony/Component/DependencyInjection/Compiler/AutowirePass.php
@@ -91,11 +91,13 @@ private function completeDefinition($id, Definition $definition)
                     try {
                         $value = $this->createAutowiredDefinition($typeHint, $id);
                     } catch (RuntimeException $e) {
-                        if (!$parameter->isDefaultValueAvailable()) {
+                        if ($parameter->allowsNull()) {
+                            $value = null;
+                        } elseif ($parameter->isDefaultValueAvailable()) {
+                            $value = $parameter->getDefaultValue();
+                        } else {
                             throw $e;
                         }
-
-                        $value = $parameter->getDefaultValue();
                     }
                 }
             } catch (\ReflectionException $reflectionException) {