diff --git a/src/Symfony/Component/DependencyInjection/Compiler/CheckDefinitionValidityPass.php b/src/Symfony/Component/DependencyInjection/Compiler/CheckDefinitionValidityPass.php
index bb87f47cddd47..c776195e2d6c6 100644
--- a/src/Symfony/Component/DependencyInjection/Compiler/CheckDefinitionValidityPass.php
+++ b/src/Symfony/Component/DependencyInjection/Compiler/CheckDefinitionValidityPass.php
@@ -44,7 +44,7 @@ public function process(ContainerBuilder $container)
             }
 
             // non-synthetic, non-abstract service has class
-            if (!$definition->isAbstract() && !$definition->isSynthetic() && !$definition->getClass() && (!$definition->getFactory() || !preg_match(FileLoader::ANONYMOUS_ID_REGEXP, $id))) {
+            if (!$definition->isAbstract() && !$definition->isSynthetic() && !$definition->getClass() && !$definition->hasTag('container.service_locator') && (!$definition->getFactory() || !preg_match(FileLoader::ANONYMOUS_ID_REGEXP, $id))) {
                 if ($definition->getFactory()) {
                     throw new RuntimeException(sprintf('Please add the class to service "%s" even if it is constructed by a factory since we might need to add method calls based on compile-time checks.', $id));
                 }
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Compiler/CheckDefinitionValidityPassTest.php b/src/Symfony/Component/DependencyInjection/Tests/Compiler/CheckDefinitionValidityPassTest.php
index ed1e300ce053c..c683fdbbc118a 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/Compiler/CheckDefinitionValidityPassTest.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/Compiler/CheckDefinitionValidityPassTest.php
@@ -37,6 +37,16 @@ public function testProcessDetectsNonSyntheticNonAbstractDefinitionWithoutClass(
         $this->process($container);
     }
 
+    public function testProcessAcceptsServiceLocatorWithoutClass()
+    {
+        $container = new ContainerBuilder();
+        $container->register('a')->addTag('container.service_locator');
+
+        $this->process($container);
+
+        $this->addToAssertionCount(1);
+    }
+
     public function testProcessDetectsFactoryWithoutClass()
     {
         $container = new ContainerBuilder();