diff --git a/sys/kern/vfs_mountroot.c b/sys/kern/vfs_mountroot.c
--- a/sys/kern/vfs_mountroot.c
+++ b/sys/kern/vfs_mountroot.c
@@ -794,7 +794,7 @@
 		ma = parse_mountroot_options(ma, opts);
 
 		error = kernel_mount(ma, MNT_ROOTFS);
-		if (error == 0 || timeout <= 0)
+		if (error == 0 || error == EILSEQ || timeout <= 0)
 			break;
 
 		if (root_mount_timeout * hz == timeout ||
diff --git a/sys/ufs/ffs/ffs_subr.c b/sys/ufs/ffs/ffs_subr.c
--- a/sys/ufs/ffs/ffs_subr.c
+++ b/sys/ufs/ffs/ffs_subr.c
@@ -35,6 +35,7 @@
 __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
+#include <sys/endian.h>
 #include <sys/limits.h>
 
 #ifndef _KERNEL
@@ -144,6 +145,7 @@
  *     EIO: non-existent or truncated superblock.
  *     EIO: error reading summary information.
  *     ENOENT: no usable known superblock found.
+ *     EILSEQ: filesystem with wrong byte order found.
  *     ENOMEM: failed to allocate space for the superblock.
  *     EINVAL: The previous newfs operation on this volume did not complete.
  *         The administrator must complete newfs before using this volume.
@@ -382,6 +384,18 @@
 	prtmsg = ((flags & UFS_NOMSG) == 0);
 	warnerr = (flags & UFS_NOWARNFAIL) == UFS_NOWARNFAIL ? 0 : ENOENT;
 	wmsg = warnerr ? "" : " (Ignored)";
+
+	/*
+	* Check for endian mismatch between machine and filesystem.
+	*/
+	if (((fs->fs_magic != FS_UFS2_MAGIC) &&
+		(bswap32(fs->fs_magic) == FS_UFS2_MAGIC)) ||
+		((fs->fs_magic != FS_UFS1_MAGIC) &&
+		(bswap32(fs->fs_magic) == FS_UFS1_MAGIC))) {
+			MPRINT("UFS superblock failed due to endian mismatch "
+				"between machine and filesystem\n");
+			return(EILSEQ);
+	}
 	/*
 	 * If just validating for recovery, then do just the minimal
 	 * checks needed for the superblock fields needed to find
@@ -627,8 +641,16 @@
 	 * failure can be avoided.
 	 */
 	flags = UFS_NOMSG | nocsum;
-	if (ffs_sbget(devfd, fsp, UFS_STDSB, flags, filltype, readfunc) == 0)
-		return (0);
+	error = ffs_sbget(devfd, fsp, UFS_STDSB, flags, filltype, readfunc);
+	/*
+	 * If successful or endian error, no need to try further.
+	 */
+	if (error == 0 || error == EILSEQ) {
+		if (msg && error == EILSEQ)
+			printf("UFS superblock failed due to endian mismatch "
+				"between machine and filesystem\n");
+		return (error);
+	}
 	/*
 	 * First try: ignoring hash failures.
 	 */
@@ -677,6 +699,7 @@
 		 * but some devices lie. So we just try a plausible range.
 		 */
 		error = ENOENT;
+		fsrbuf = NULL;
 		for (secsize = dbtob(1); secsize <= SBLOCKSIZE; secsize *= 2)
 			if ((error = (*readfunc)(devfd, (SBLOCK_UFS2 - secsize),
 			    &fsrbuf, secsize)) == 0)