--- a/sys/vfs/hpfs/hpfs.h
+++ b/sys/vfs/hpfs/hpfs.h
@@ -206,7 +206,7 @@
 	u_int8_t	fn_uid[0x10];
 	u_int16_t	fn_intoff;
 	u_int8_t	fn_1dasdthr;
 	u_int8_t	fn_dasdthr;
 	u_int32_t	fn_dasdlim;
 	u_int32_t	fn_dasdusage;
-	u_int8_t	fn_int[0x13c];
+	u_int8_t	fn_int[0x138];	/* struct fnode must end exactly at FNODESIZE (512) */
 };
 
 /*