diff --git a/src/htsmsg.h b/src/htsmsg.h
index 4d59c6c..44f445d 100644
--- a/src/htsmsg.h
+++ b/src/htsmsg.h
@@ -18,6 +18,7 @@
 
 #pragma once
 #include <stdlib.h>
+#include <unistd.h>
 #include <inttypes.h>
 #include "queue.h"