diff --git a/lib/libarchive/archive_write_disk_private.h b/lib/libarchive/archive_write_disk_private.h
index 562229b2e53d..8ec6391e8b91 100644
--- a/lib/libarchive/archive_write_disk_private.h
+++ b/lib/libarchive/archive_write_disk_private.h
@@ -26,6 +26,10 @@
  * $FreeBSD$
  */
 
+#ifndef __LIBARCHIVE_BUILD
+#error This header is only to be used internally to libarchive.
+#endif
+
 #ifndef ARCHIVE_WRITE_DISK_PRIVATE_H_INCLUDED
 #define ARCHIVE_WRITE_DISK_PRIVATE_H_INCLUDED