diff --git a/ares/setup_once.h b/ares/setup_once.h
index 8f24d8c486..224ab692ae 100644
--- a/ares/setup_once.h
+++ b/ares/setup_once.h
@@ -77,9 +77,6 @@
                                    (RECV_TYPE_ARG4)(SEND_4TH_ARG))
 #endif
 #else /* HAVE_RECV */
-#ifdef MSDOS
-#define sread(x,y,z) (ssize_t)read_s((int)(x), (char *)(y), (int)(z))
-#endif
 #ifndef sread
   /* */
   Error Missing_definition_of_macro_sread
@@ -104,9 +101,6 @@
                                     (SEND_TYPE_ARG4)(SEND_4TH_ARG))
 #endif
 #else /* HAVE_SEND */
-#ifdef MSDOS
-#define swrite(x,y,z) (ssize_t)write_s((int)(x), (char *)(y), (int)(z))
-#endif
 #ifndef swrite
   /* */
   Error Missing_definition_of_macro_swrite