diff --git a/hash.h b/hash.h
index acf17bb..3e7854b 100644
--- a/hash.h
+++ b/hash.h
@@ -13,6 +13,13 @@
  * them can use shifts and additions instead of multiplications for
  * machines where multiplications are slow.
  */
+
+#ifdef __WORDSIZE
+#define BITS_PER_LONG	__WORDSIZE
+#else
+#define BITS_PER_LONG	32
+#endif
+
 #if BITS_PER_LONG == 32
 /* 2^31 + 2^29 - 2^25 + 2^22 - 2^19 - 2^16 + 1 */
 #define GOLDEN_RATIO_PRIME 0x9e370001UL