diff --git a/tests/pkg_libcose/main.c b/tests/pkg_libcose/main.c
index 6a6de802eb..1f64f1bb32 100644
--- a/tests/pkg_libcose/main.c
+++ b/tests/pkg_libcose/main.c
@@ -22,6 +22,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 
 #include "cose.h"
 #include "cose/sign.h"