diff --git a/Resources/doc/index.rst b/Resources/doc/index.rst
index e637fb0..308f75f 100644
--- a/Resources/doc/index.rst
+++ b/Resources/doc/index.rst
@@ -47,7 +47,7 @@ Configuration
 ::
 
     jms_aop:
-        cache_dir: %kernel.cache_dir%/jms_aop
+        cache_dir: '%kernel.cache_dir%/jms_aop'
 
 
 Usage