diff --git a/Lib/functools.py b/Lib/functools.py
index fdc9c79098b..3bffbacae47 100644
--- a/Lib/functools.py
+++ b/Lib/functools.py
@@ -96,6 +96,7 @@ def total_ordering(cls):
 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 76b42b85205..b9751b7436b 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -84,6 +84,8 @@ Library
 - Issue #11371: Mark getopt error messages as localizable.  Patch by Filip
   Gruszczyński.
 
+- 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.