diff --git a/Lib/test/test_deque.py b/Lib/test/test_deque.py
index a8487d2d955..e782b99203e 100644
--- a/Lib/test/test_deque.py
+++ b/Lib/test/test_deque.py
@@ -536,7 +536,7 @@ class TestBasic(unittest.TestCase):
 
     @support.cpython_only
     def test_sizeof(self):
-        BLOCKLEN = 62
+        BLOCKLEN = 64
         basesize = support.calcobjsize('2P4nlP')
         blocksize = struct.calcsize('2P%dP' % BLOCKLEN)
         self.assertEqual(object.__sizeof__(deque()), basesize)
diff --git a/Modules/_collectionsmodule.c b/Modules/_collectionsmodule.c
index b9224754db4..781949d48f2 100644
--- a/Modules/_collectionsmodule.c
+++ b/Modules/_collectionsmodule.c
@@ -14,7 +14,7 @@
  * division/modulo computations during indexing.
  */
 
-#define BLOCKLEN 62
+#define BLOCKLEN 64
 #define CENTER ((BLOCKLEN - 1) / 2)
 
 /* A `dequeobject` is composed of a doubly-linked list of `block` nodes.