diff --git a/newlib/libc/include/sys/select.h b/newlib/libc/include/sys/select.h
index 93d0b79bf..8b5675640 100644
--- a/newlib/libc/include/sys/select.h
+++ b/newlib/libc/include/sys/select.h
@@ -30,6 +30,8 @@ typedef	__sigset_t	sigset_t;
 #ifndef FD_SETSIZE
 # ifdef __CYGWIN__
 #  define FD_SETSIZE	1024
+# elifdef __rtems__
+#  define FD_SETSIZE	256
 # else
 #  define FD_SETSIZE	64
 # endif