diff --git a/src/libsodium/include/sodium/private/common.h b/src/libsodium/include/sodium/private/common.h
index 1d615557..4b01c8a0 100644
--- a/src/libsodium/include/sodium/private/common.h
+++ b/src/libsodium/include/sodium/private/common.h
@@ -252,6 +252,9 @@ xor_buf(unsigned char *out, const unsigned char *in, size_t n)
 
 # elif defined(_M_ARM64)
 
+#  ifndef __ARM_ARCH
+#   define __ARM_ARCH 1
+#  endif
 #  ifndef __ARM_NEON
 #   define __ARM_NEON 1
 #  endif