--- origsrc/libusb-1.0.21/libusb/io.c	2016-10-25 18:07:38.000000000 +0200
+++ src/libusb-1.0.21/libusb/io.c	2020-02-02 06:33:05.141074300 +0100
@@ -27,6 +27,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <time.h>
+#include <unistd.h>
 #ifdef HAVE_SIGNAL_H
 #include <signal.h>
 #endif