diff --git a/src/Symfony/Components/DependencyInjection/Dumper/PhpDumper.php b/src/Symfony/Components/DependencyInjection/Dumper/PhpDumper.php
index 9faecef2f149..395d4462bce3 100644
--- a/src/Symfony/Components/DependencyInjection/Dumper/PhpDumper.php
+++ b/src/Symfony/Components/DependencyInjection/Dumper/PhpDumper.php
@@ -87,6 +87,10 @@ protected function addServiceInstance($id, $definition)
     {
         $class = $this->dumpValue($definition->getClass());
 
+        if (0 === strpos($class, "'") && !preg_match('/^\'[a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*\'$/', $class)) {
+            throw new \InvalidArgumentException(sprintf('"%s" is not a valid class name.', $class));
+        }
+
         $arguments = array();
         foreach ($definition->getArguments() as $value) {
             $arguments[] = $this->dumpValue($value);