Index: src/net/conn_plain.c
--- src/net/conn_plain.c.orig	2018-12-05 16:48:06.871939000 +0100
+++ src/net/conn_plain.c	2018-12-05 16:48:35.152879000 +0100
@@ -7,6 +7,7 @@
 #include <unistd.h>
 #include <postgres.h>
 #include <pg_config.h>
+#include <sys/types.h>
 #include <sys/socket.h>
 #include <sys/time.h>