diff --git a/sys/sys/cdefs.h b/sys/sys/cdefs.h
index 26a3623030d68939a45d60f88748a8a1fd02dd48..4e2b59754a8837190807a11b0756fd4832176d7d 100644
--- a/sys/sys/cdefs.h
+++ b/sys/sys/cdefs.h
@@ -35,8 +35,8 @@
  * $FreeBSD: releng/12.2/sys/sys/cdefs.h 337399 2018-08-06 23:51:08Z jhb $
  */
 
-#ifndef	_SYS_CDEFS_H_
-#define	_SYS_CDEFS_H_
+#ifndef	_SYS_CDEFS_H__
+#define	_SYS_CDEFS_H__
 
 /*
  * Testing against Clang-specific extensions.
@@ -883,4 +883,7 @@
 #define	__guarded_by(x)		__lock_annotate(guarded_by(x))
 #define	__pt_guarded_by(x)	__lock_annotate(pt_guarded_by(x))
 
-#endif /* !_SYS_CDEFS_H_ */
+#include_next <sys/cdefs.h>
+typedef long long loff_t;
+
+#endif /* !_SYS_CDEFS_H__ */