diff --git a/src/nspawn/nspawn-patch-uid.h b/src/nspawn/nspawn-patch-uid.h
index 55d0990016..ff6a7b7647 100644
--- a/src/nspawn/nspawn-patch-uid.h
+++ b/src/nspawn/nspawn-patch-uid.h
@@ -1,3 +1,5 @@
+#pragma once
+
 /***
   This file is part of systemd.