diff --git a/Objects/obmalloc.c b/Objects/obmalloc.c
index 46e8427..885ad53 100644
--- a/Objects/obmalloc.c
+++ b/Objects/obmalloc.c
@@ -788,8 +788,14 @@
  *
  * You shouldn't change this unless you know what you are doing.
  */
+
+#if SIZEOF_VOID_P > 4
+#define ALIGNMENT              16               /* must be 2^N */
+#define ALIGNMENT_SHIFT         4
+#else
 #define ALIGNMENT               8               /* must be 2^N */
 #define ALIGNMENT_SHIFT         3
+#endif
 
 /* Return the number of bytes in size class I, as a uint. */
 #define INDEX2SIZE(I) (((uint)(I) + 1) << ALIGNMENT_SHIFT)