diff --git a/sshbn.h b/sshbn.h
index a043241e..9366f614 100644
--- a/sshbn.h
+++ b/sshbn.h
@@ -26,7 +26,7 @@
  * using the same 'two machine registers' kind of code generation that
  * 32-bit targets use for 64-bit ints. If we have one of these, we can
  * use a 64-bit BignumInt and a 128-bit BignumDblInt. */
-typedef __uint64_t BignumInt;
+typedef unsigned long long BignumInt;
 typedef __uint128_t BignumDblInt;
 #define BIGNUM_INT_MASK  0xFFFFFFFFFFFFFFFFULL
 #define BIGNUM_TOP_BIT   0x8000000000000000ULL