Index: src/bin/scripts/vacuumdb.c
--- src/bin/scripts/vacuumdb.c.orig
+++ src/bin/scripts/vacuumdb.c
@@ -10,6 +10,8 @@
  *-------------------------------------------------------------------------
  */
 
+#include <sys/select.h> /* FD_SETSIZE */
+
 #include "postgres_fe.h"
 
 #include <limits.h>