--- a/src/tools/pgproto/read.c
+++ b/src/tools/pgproto/read.c
@@ -26,6 +26,7 @@
 #include "pgproto/fe_memutils.h"
 #include <libpq-fe.h>
 #include "pgproto/read.h"
+#include <sys/select.h>
 
 static char read_char(PGconn *conn);
 static int	read_int32(PGconn *conn);