diff --git a/peps/pep-0667.rst b/peps/pep-0667.rst
index cbe1b5d26..97c98efb3 100644
--- a/peps/pep-0667.rst
+++ b/peps/pep-0667.rst
@@ -282,7 +282,7 @@ They serve only to illustrate the proposed design.
     class FrameLocalsProxy:
         "Implements collections.MutableMapping."
 
-        __slots__ "_frame"
+        __slots__ = ("_frame", )
 
         def __init__(self, frame:FrameType):
             self._frame = frame