diff --git a/src/string_bytes.cc b/src/string_bytes.cc
index 7ba2caf93db..a2ee589bfaa 100644
--- a/src/string_bytes.cc
+++ b/src/string_bytes.cc
@@ -387,7 +387,7 @@ static bool contains_non_ascii(const char* src, size_t len) {
   }
 
 
-#if BITS_PER_LONG == 64
+#if defined(__x86_64__) || defined(_WIN64)
   const uintptr_t mask = 0x8080808080808080ll;
 #else
   const uintptr_t mask = 0x80808080l;
@@ -440,7 +440,7 @@ static void force_ascii(const char* src, char* dst, size_t len) {
     }
   }
 
-#if BITS_PER_LONG == 64
+#if defined(__x86_64__) || defined(_WIN64)
   const uintptr_t mask = ~0x8080808080808080ll;
 #else
   const uintptr_t mask = ~0x80808080l;