diff --git a/src/bin/scripts/scripts_parallel.c b/src/bin/scripts/scripts_parallel.c
index 55bda9044b..97435160e9 100644
--- a/src/bin/scripts/scripts_parallel.c
+++ b/src/bin/scripts/scripts_parallel.c
@@ -12,6 +12,10 @@
  *-------------------------------------------------------------------------
  */
 
+#ifdef WIN32
+#define FD_SETSIZE 1024			/* must set before winsock2.h is included */
+#endif
+
 #include "postgres_fe.h"
 
 #ifdef HAVE_SYS_SELECT_H