diff --git a/cryptonite.cabal b/cryptonite.cabal
index 9901670..e670a53 100644
--- a/cryptonite.cabal
+++ b/cryptonite.cabal
@@ -169,7 +169,11 @@ Library
   if (arch(i386) || arch(x86_64))
     CPP-options: -DARCH_IS_LITTLE_ENDIAN
 
+  if arch(i386)
+    CPP-options: -DARCH_X86
+
   if arch(x86_64)
+    CPP-options:    -DARCH_X86_64
     CPP-options:    -DSUPPORT_RDRAND
     Other-modules:  Crypto.Random.Entropy.RDRand
     c-sources:      cbits/cryptonite_rdrand.c