diff --git a/src/vmspawn/vmspawn-register.c b/src/vmspawn/vmspawn-register.c
index 20e6def360..e60467496a 100644
--- a/src/vmspawn/vmspawn-register.c
+++ b/src/vmspawn/vmspawn-register.c
@@ -1,5 +1,7 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 
+#include <unistd.h>
+
 #include "sd-bus.h"
 #include "sd-id128.h"
 #include "sd-json.h"