diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 3b447531660..ae2ff85942b 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,7 @@
+Wed Jun 30 20:06:46 1993  Jim Kingdon  (kingdon@lioth.cygnus.com)
+
+	* config/vax/xm-vaxult2.h: Define FD_SET and FD_ZERO.
+
 Tue Jun 29 11:02:58 1993  Jim Kingdon  (kingdon@lioth.cygnus.com)
 
 	* inftarg.c: Remove unused include of terminal.h.
diff --git a/gdb/config/vax/xm-vaxult2.h b/gdb/config/vax/xm-vaxult2.h
index 5bbed5b3de7..f3e2550ba8a 100644
--- a/gdb/config/vax/xm-vaxult2.h
+++ b/gdb/config/vax/xm-vaxult2.h
@@ -5,3 +5,8 @@ extern char *strdup();
 
 #define MEM_FNS_DECLARED
 #define NO_PTRACE_H
+
+/* Old versions of ultrix have fd_set but not the FD_* macros.  */
+
+#define FD_SET(bit,fdsetp) ((fdsetp)->fds_bits[(n) / 32] |= (1 << ((n) % 32)))
+#define FD_ZERO(fdsetp) memset (fdsetp, 0, sizeof (*fdsetp))