diff --git a/src/Symfony/Component/Form/AbstractType.php b/src/Symfony/Component/Form/AbstractType.php
index 3509db5d94..1a9cfd75be 100644
--- a/src/Symfony/Component/Form/AbstractType.php
+++ b/src/Symfony/Component/Form/AbstractType.php
@@ -52,7 +52,7 @@ abstract class AbstractType implements FormTypeInterface
      */
     public function getBlockPrefix()
     {
-        return StringUtil::fqcnToBlockPrefix(\get_class($this));
+        return StringUtil::fqcnToBlockPrefix(\get_class($this)) ?: '';
     }
 
     /**