diff --git a/libc/kernel/common/linux/stddef.h b/libc/kernel/common/linux/stddef.h
index 5412f475d..cca408ca5 100644
--- a/libc/kernel/common/linux/stddef.h
+++ b/libc/kernel/common/linux/stddef.h
@@ -7,25 +7,24 @@
  ***   structures, and macros generated from the original header, and thus,
  ***   contains no copyrightable information.
  ***
+ ***   To edit the content of this header, modify the corresponding
+ ***   source file (e.g. under external/kernel-headers/original/) then
+ ***   run bionic/libc/kernel/tools/update_all.py
+ ***
+ ***   Any manual change here will be lost the next time this script will
+ ***   be run. You've been warned!
+ ***
  ****************************************************************************
  ****************************************************************************/
 #ifndef _LINUX_STDDEF_H
 #define _LINUX_STDDEF_H
-
 #include <linux/compiler.h>
-
 #undef NULL
+/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
 #ifdef __cplusplus
 #define NULL 0
 #else
 #define NULL ((void *)0)
+/* WARNING: DO NOT EDIT, AUTO-GENERATED CODE - SEE TOP FOR INSTRUCTIONS */
 #endif
-
-#undef offsetof
-#ifdef __compiler_offsetof
-#define offsetof(TYPE,MEMBER) __compiler_offsetof(TYPE,MEMBER)
-#else
-#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
-#endif
-
 #endif