diff --git a/src/hlr_ussd.h b/src/hlr_ussd.h
index d1b9fe05..67e5d0d0 100644
--- a/src/hlr_ussd.h
+++ b/src/hlr_ussd.h
@@ -1,3 +1,5 @@
+#pragma once
+
 #include <stdint.h>
 #include <osmocom/core/linuxlist.h>
 #include <osmocom/gsm/gsup.h>