Index: rocs/impl/unx/uthread.c
--- rocs/impl/unx/uthread.c.orig
+++ rocs/impl/unx/uthread.c
@@ -26,6 +26,7 @@
 #include <stddef.h>
 #include <signal.h>
 #include <errno.h>
+#include <unistd.h>
 
 #include <pthread.h>
 #include <sched.h>
