diff --git a/crypto/bn/bn.h b/crypto/bn/bn.h
index 9f4668a51da741eb390445d2cfacea1f95b7efbd..670584ad74a7cbe683c0df7d8045dad624ae0722 100644
--- a/crypto/bn/bn.h
+++ b/crypto/bn/bn.h
@@ -167,7 +167,7 @@ extern "C" {
 #ifdef THIRTY_TWO_BIT
 #ifdef BN_LLONG
 # if defined(OPENSSL_SYS_WIN32) && !defined(__GNUC__)
-#  define BN_ULLONG	unsigned _int64
+#  define BN_ULLONG	unsigned __int64
 # else
 #  define BN_ULLONG	unsigned long long
 # endif