diff --git a/curve25519-donna/curve25519-donna-portable.h b/curve25519-donna/curve25519-donna-portable.h
index 71da697d54..0f428730e8 100644
--- a/curve25519-donna/curve25519-donna-portable.h
+++ b/curve25519-donna/curve25519-donna-portable.h
@@ -13,6 +13,7 @@
 	#define inline __forceinline
 	#define DONNA_INLINE __forceinline
 	#define DONNA_NOINLINE __declspec(noinline)
+	#undef ALIGN
 	#define ALIGN(x) __declspec(align(x))
 	#define ROTL32(a,b) _rotl(a,b)
 	#define ROTR32(a,b) _rotr(a,b)
@@ -20,6 +21,7 @@
 	#include <sys/param.h>
 	#define DONNA_INLINE inline __attribute__((always_inline))
 	#define DONNA_NOINLINE __attribute__((noinline))
+	#undef ALIGN
 	#define ALIGN(x) __attribute__((aligned(x)))
 	#define ROTL32(a,b) (((a) << (b)) | ((a) >> (32 - b)))
 	#define ROTR32(a,b) (((a) >> (b)) | ((a) << (32 - b)))