diff --git a/lib/libarchive/archive_string.h b/lib/libarchive/archive_string.h
index 56ca7ca31805..68fbf167e734 100644
--- a/lib/libarchive/archive_string.h
+++ b/lib/libarchive/archive_string.h
@@ -26,6 +26,10 @@
  *
  */
 
+#ifndef __LIBARCHIVE_BUILD
+#error This header is only to be used internally to libarchive.
+#endif
+
 #ifndef ARCHIVE_STRING_H_INCLUDED
 #define	ARCHIVE_STRING_H_INCLUDED