diff --git a/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/Compiler/UnusedTagsPass.php b/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/Compiler/UnusedTagsPass.php
index ed852fd041942..7fc7b4f363826 100644
--- a/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/Compiler/UnusedTagsPass.php
+++ b/src/Symfony/Bundle/FrameworkBundle/DependencyInjection/Compiler/UnusedTagsPass.php
@@ -65,13 +65,16 @@ public function process(ContainerBuilder $container)
 
             // check for typos
             $candidates = array();
-            foreach ($tags as $definedTag) {
-                if ($definedTag === $tag) {
-                    continue;
-                }
 
-                if (false !== strpos($definedTag, $tag) || levenshtein($tag, $definedTag) <= strlen($tag) / 3) {
-                    $candidates[] = $definedTag;
+            if (null !== $tag && '' !== $tag) {
+                foreach ($tags as $definedTag) {
+                    if ($definedTag === $tag) {
+                        continue;
+                    }
+
+                    if (false !== strpos($definedTag, $tag) || levenshtein($tag, $definedTag) <= strlen($tag) / 3) {
+                        $candidates[] = $definedTag;
+                    }
                 }
             }
 
diff --git a/src/Symfony/Bundle/FrameworkBundle/Tests/DependencyInjection/Compiler/UnusedTagsPassTest.php b/src/Symfony/Bundle/FrameworkBundle/Tests/DependencyInjection/Compiler/UnusedTagsPassTest.php
index f354007bb982d..fbbe792eb85b4 100644
--- a/src/Symfony/Bundle/FrameworkBundle/Tests/DependencyInjection/Compiler/UnusedTagsPassTest.php
+++ b/src/Symfony/Bundle/FrameworkBundle/Tests/DependencyInjection/Compiler/UnusedTagsPassTest.php
@@ -12,6 +12,7 @@
 namespace Symfony\Bundle\FrameworkBundle\Tests\DependencyInjection\Compiler;
 
 use Symfony\Bundle\FrameworkBundle\DependencyInjection\Compiler\UnusedTagsPass;
+use Symfony\Component\DependencyInjection\ContainerBuilder;
 
 class UnusedTagsPassTest extends \PHPUnit_Framework_TestCase
 {
@@ -49,4 +50,23 @@ public function testProcess()
 
         $pass->process($container);
     }
+
+    public function testEmptyTagNameIsIgnored()
+    {
+        $pass = new UnusedTagsPass();
+
+        $container = new ContainerBuilder();
+        $definition = $container->register('foo');
+        $definition->addTag('', array('bar' => 'baz'));
+        $definition->addTag('foo');
+
+        $pass->process($container);
+
+        $this->assertMessageIsLogged($container, 'Tag "foo" was defined on service(s) "foo", but was never used.');
+    }
+
+    private function assertMessageIsLogged(ContainerBuilder $container, $message)
+    {
+        $this->assertContains('Symfony\Bundle\FrameworkBundle\DependencyInjection\Compiler\UnusedTagsPass: '.$message, $container->getCompiler()->getLog());
+    }
 }