diff --git a/src/Symfony/Component/Form/AbstractType.php b/src/Symfony/Component/Form/AbstractType.php
index 3509db5d94a9..1a9cfd75be7f 100644
--- a/src/Symfony/Component/Form/AbstractType.php
+++ b/src/Symfony/Component/Form/AbstractType.php
@@ -52,7 +52,7 @@ public function configureOptions(OptionsResolver $resolver)
      */
     public function getBlockPrefix()
     {
-        return StringUtil::fqcnToBlockPrefix(\get_class($this));
+        return StringUtil::fqcnToBlockPrefix(\get_class($this)) ?: '';
     }
 
     /**