diff --git a/src/util/mpz.cpp b/src/util/mpz.cpp
index d3e9941d3..936520f22 100644
--- a/src/util/mpz.cpp
+++ b/src/util/mpz.cpp
@@ -41,7 +41,6 @@ Revision History:
 
 #if defined(_MP_GMP)
 // Use LEHMER only if not using GMP
-// LEHMER assumes 32-bit digits, so it cannot be used with MSBIGNUM library + 64-bit binary
 #define EUCLID_GCD
 #else
 #define LEHMER_GCD
@@ -50,7 +49,7 @@ Revision History:
 
 #if defined(__GNUC__)
 #define _trailing_zeros32(X) __builtin_ctz(X)
-#elif defined(_WINDOWS) && !defined(_M_ARM) && !defined(_M_ARM64) && !defined(__MINGW32__)
+#elif defined(_WINDOWS) && defined(_M_X64)
 // This is needed for _tzcnt_u32 and friends.
 #include <immintrin.h>
 #define _trailing_zeros32(X) _tzcnt_u32(X)
@@ -62,7 +61,7 @@ static uint32_t _trailing_zeros32(uint32_t x) {
 }
 #endif
 
-#if (defined(__LP64__) || defined(_WIN64)) && !defined(_M_ARM) && !defined(_M_ARM64)
+#if (defined(__LP64__) || defined(_WIN64)) && defined(_M_X64)
  #if defined(__GNUC__)
  #define _trailing_zeros64(X) __builtin_ctzll(X)
  #else