diff --git a/include/ruby/io/buffer.h b/include/ruby/io/buffer.h
index b044db0539..e4d98bf051 100644
--- a/include/ruby/io/buffer.h
+++ b/include/ruby/io/buffer.h
@@ -69,14 +69,10 @@ enum rb_io_buffer_endian {
     RB_IO_BUFFER_LITTLE_ENDIAN = 4,
     RB_IO_BUFFER_BIG_ENDIAN = 8,
 
-#if defined(__BYTE_ORDER__) && __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
-    RB_IO_BUFFER_HOST_ENDIAN = RB_IO_BUFFER_LITTLE_ENDIAN,
-#elif defined(__BYTE_ORDER__) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+#if defined(WORDS_BIGENDIAN)
     RB_IO_BUFFER_HOST_ENDIAN = RB_IO_BUFFER_BIG_ENDIAN,
-#elif defined(REG_DWORD) && REG_DWORD == REG_DWORD_LITTLE_ENDIAN
+#else
     RB_IO_BUFFER_HOST_ENDIAN = RB_IO_BUFFER_LITTLE_ENDIAN,
-#elif defined(REG_DWORD) && REG_DWORD == REG_DWORD_BIG_ENDIAN
-    RB_IO_BUFFER_HOST_ENDIAN = RB_IO_BUFFER_BIG_ENDIAN,
 #endif
 
     RB_IO_BUFFER_NETWORK_ENDIAN = RB_IO_BUFFER_BIG_ENDIAN