--- sys/fs/cd9660/cd9660_vnops.c.orig
+++ sys/fs/cd9660/cd9660_vnops.c
@@ -758,6 +758,9 @@
 	/* NOTREACHED */
 }
 
+_Static_assert(sizeof(struct ifid) <= sizeof(struct fid),
+    "struct ifid must be no larger than struct fid");
+
 /*
  * Vnode pointer to File handle
  */
--- sys/fs/cd9660/iso.h.orig
+++ sys/fs/cd9660/iso.h
@@ -267,7 +267,7 @@
 	u_short		ifid_pad;
 	cd_ino_t	ifid_ino;
 	long		ifid_start;
-};
+} __packed;
 
 #define VFSTOISOFS(mp)	((struct iso_mnt *)((mp)->mnt_data))
 
--- sys/fs/ext2fs/ext2_vnops.c.orig
+++ sys/fs/ext2fs/ext2_vnops.c
@@ -1889,6 +1889,8 @@
 {
 	struct inode *ip;
 	struct ufid *ufhp;
+	_Static_assert(sizeof(struct ufid) <= sizeof(struct fid),
+	    "struct ufid cannot be larger than struct fid");
 
 	ip = VTOI(ap->a_vp);
 	ufhp = (struct ufid *)ap->a_fhp;
--- sys/fs/ext2fs/inode.h.orig
+++ sys/fs/ext2fs/inode.h
@@ -191,7 +191,7 @@
 	uint16_t ufid_pad;		/* Force 32-bit alignment. */
 	ino_t	ufid_ino;		/* File number (ino). */
 	uint32_t ufid_gen;		/* Generation number. */
-};
+} __packed;
 #endif	/* _KERNEL */
 
 #endif	/* !_FS_EXT2FS_INODE_H_ */