diff --git a/hwaccess.c b/hwaccess.c
index 44d7871..f754166 100644
--- a/hwaccess.c
+++ b/hwaccess.c
@@ -21,6 +21,7 @@
 #include <stdint.h>
 #include <string.h>
 #include <stdlib.h>
+#include <unistd.h>
 #include <fcntl.h>
 #include <sys/types.h>
 #include <errno.h>