diff --git a/src/Symfony/Bundle/FrameworkBundle/Command/ServerRunCommand.php b/src/Symfony/Bundle/FrameworkBundle/Command/ServerRunCommand.php
index d2255e50be..f47283a70a 100644
--- a/src/Symfony/Bundle/FrameworkBundle/Command/ServerRunCommand.php
+++ b/src/Symfony/Bundle/FrameworkBundle/Command/ServerRunCommand.php
@@ -66,6 +66,9 @@ If you have custom docroot directory layout, you can specify your own
 router script using <info>--router</info> option:
 
   <info>%command.full_name% --router=app/config/router.php</info>
+  
+Specifing a router script is required when the used environment is not "dev" or
+"prod".
 
 See also: http://www.php.net/manual/en/features.commandline.webserver.php
 EOF