diff --git a/Lib/functools.py b/Lib/functools.py
index 03de69a..e92a2fc 100644
--- a/Lib/functools.py
+++ b/Lib/functools.py
@@ -96,6 +96,7 @@
 def cmp_to_key(mycmp):
     """Convert a cmp= function into a key= function"""
     class K(object):
+        __slots__ = ['obj']
         def __init__(self, obj, *args):
             self.obj = obj
         def __lt__(self, other):
diff --git a/Misc/NEWS b/Misc/NEWS
index 0bf7550..5589daf 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -49,6 +49,8 @@
 Library
 -------
 
+- Issue #11628: cmp_to_key generated class should use __slots__
+
 - Issue #5537: Fix time2isoz() and time2netscape() functions of
   httplib.cookiejar for expiration year greater than 2038 on 32-bit systems.