diff --git a/include/linux/if_phonet.h b/include/linux/if_phonet.h
index 7e989216ec17e334922728f32cbab41ac9f38470..d70034bcec059800d9d972a6d37096b38cb4809c 100644
--- a/include/linux/if_phonet.h
+++ b/include/linux/if_phonet.h
@@ -5,14 +5,15 @@
  *
  * Copyright (C) 2008 Nokia Corporation. All rights reserved.
  */
+#ifndef LINUX_IF_PHONET_H
+#define LINUX_IF_PHONET_H
 
-#define PHONET_HEADER_LEN	8	/* Phonet header length */
-
-#define PHONET_MIN_MTU		6
-/* 6 bytes header + 65535 bytes payload */
-#define PHONET_MAX_MTU		65541
+#define PHONET_MIN_MTU		6	/* pn_length = 0 */
+#define PHONET_MAX_MTU		65541	/* pn_length = 0xffff */
 #define PHONET_DEV_MTU		PHONET_MAX_MTU
 
 #ifdef __KERNEL__
 extern struct header_ops phonet_header_ops;
 #endif
+
+#endif