mod_cart_index.phtml error

Hello,

i have an error with index.php?_url=/cart "An exception has been thrown during the rendering of a template ("Model not found") in "mod_cart_index.phtml" at line 7."

the problem is {% set cart = guest.cart_get %}, i try {% set cart = guest.cart_get() %} but i get the same error.

Can you help me ? Thanks !