diff --git a/libc/kernel/uapi/linux/stddef.h b/libc/kernel/uapi/linux/stddef.h
index d5cdf80..6bc6925 100644
--- a/libc/kernel/uapi/linux/stddef.h
+++ b/libc/kernel/uapi/linux/stddef.h
@@ -16,9 +16,12 @@
  ***
  ****************************************************************************
  ****************************************************************************/
+#ifndef _UAPI_LINUX_STDDEF_H
+#define _UAPI_LINUX_STDDEF_H
 #include <linux/compiler_types.h>
 #ifndef __always_inline
 #define __always_inline inline
 #endif
 #define __struct_group(TAG,NAME,ATTRS,MEMBERS...) union { struct { MEMBERS } ATTRS; struct TAG { MEMBERS } ATTRS NAME; }
 #define __DECLARE_FLEX_ARRAY(TYPE,NAME) struct { struct { } __empty_ ##NAME; TYPE NAME[]; }
+#endif