diff --git a/sys/gnu/ext2fs/ext2_fs.h b/sys/gnu/ext2fs/ext2_fs.h
index c7262e98cbf7..64aff0d17bfc 100644
--- a/sys/gnu/ext2fs/ext2_fs.h
+++ b/sys/gnu/ext2fs/ext2_fs.h
@@ -101,9 +101,6 @@
 /*
  * The second extended file system magic number
  */
-#ifndef notyet
-#define EXT2_PRE_02B_MAGIC	0xEF51
-#endif
 #define EXT2_SUPER_MAGIC	0xEF53
 
 /*
diff --git a/sys/gnu/ext2fs/ext2_vfsops.c b/sys/gnu/ext2fs/ext2_vfsops.c
index 90536828299a..1865dbb187a9 100644
--- a/sys/gnu/ext2fs/ext2_vfsops.c
+++ b/sys/gnu/ext2fs/ext2_vfsops.c
@@ -107,6 +107,8 @@ VFS_SET(ext2fs_vfsops, ext2fs, 0);
 
 static int ext2fs_inode_hash_lock;
 
+static int	ext2_check_sb_compat __P((struct ext2_super_block *es,
+					  dev_t dev, int ronly));
 static int	compute_sb_data __P((struct vnode * devvp,
 				     struct ext2_super_block * es,
 				     struct ext2_sb_info * fs));
@@ -365,6 +367,36 @@ static int ext2_check_descriptors (struct ext2_sb_info * sb)
         return 1;
 }
 
+static int
+ext2_check_sb_compat(es, dev, ronly)
+	struct ext2_super_block *es;
+	dev_t dev;
+	int ronly;
+{
+
+	if (es->s_magic != EXT2_SUPER_MAGIC) {
+		printf("ext2fs: %s: wrong magic number %#x (expected %#x)\n",
+		    devtoname(dev), es->s_magic, EXT2_SUPER_MAGIC);
+		return (1);
+	}
+	if (es->s_rev_level > EXT2_GOOD_OLD_REV) {
+		if (es->s_feature_incompat & ~EXT2_FEATURE_INCOMPAT_SUPP) {
+			printf(
+"WARNING: mount of %s denied due to unsupported optional features\n",
+			    devtoname(dev));
+			return (1);
+		}
+		if (!ronly &&
+		    (es->s_feature_ro_compat & ~EXT2_FEATURE_RO_COMPAT_SUPP)) {
+			printf(
+"WARNING: R/W mount of %s denied due to unsupported optional features\n",
+			    devtoname(dev));
+			return (1);
+		}
+	}
+	return (0);
+}
+
 /*
  * this computes the fields of the  ext2_sb_info structure from the
  * data in the ext2_super_block structure read in
@@ -506,14 +538,7 @@ ext2_reload(mountp, cred, p)
 	if ((error = bread(devvp, SBLOCK, SBSIZE, NOCRED, &bp)) != 0)
 		return (error);
 	es = (struct ext2_super_block *)bp->b_data;
-	if (es->s_magic != EXT2_SUPER_MAGIC) {
-		if(es->s_magic == EXT2_PRE_02B_MAGIC)
-		    printf("This filesystem bears the magic number of a pre "
-			   "0.2b version of ext2. This is not supported by "
-			   "Lites.\n");
-		else
-		    printf("Wrong magic number: %x (expected %x for ext2 fs\n",
-			es->s_magic, EXT2_SUPER_MAGIC);
+	if (ext2_check_sb_compat(es, devvp->v_rdev, 0) != 0) {
 		brelse(bp);
 		return (EIO);		/* XXX needs translation */
 	}
@@ -629,14 +654,7 @@ ext2_mountfs(devvp, mp, p)
 	if ((error = bread(devvp, SBLOCK, SBSIZE, NOCRED, &bp)) != 0)
 		goto out;
 	es = (struct ext2_super_block *)bp->b_data;
-	if (es->s_magic != EXT2_SUPER_MAGIC) {
-		if(es->s_magic == EXT2_PRE_02B_MAGIC)
-		    printf("This filesystem bears the magic number of a pre "
-			   "0.2b version of ext2. This is not supported by "
-			   "Lites.\n");
-		else
-		    printf("Wrong magic number: %x (expected %x for EXT2FS)\n",
-			es->s_magic, EXT2_SUPER_MAGIC);
+	if (ext2_check_sb_compat(es, dev, ronly) != 0) {
 		error = EINVAL;		/* XXX needs translation */
 		goto out;
 	}
diff --git a/sys/gnu/fs/ext2fs/ext2_fs.h b/sys/gnu/fs/ext2fs/ext2_fs.h
index c7262e98cbf7..64aff0d17bfc 100644
--- a/sys/gnu/fs/ext2fs/ext2_fs.h
+++ b/sys/gnu/fs/ext2fs/ext2_fs.h
@@ -101,9 +101,6 @@
 /*
  * The second extended file system magic number
  */
-#ifndef notyet
-#define EXT2_PRE_02B_MAGIC	0xEF51
-#endif
 #define EXT2_SUPER_MAGIC	0xEF53
 
 /*
diff --git a/sys/gnu/fs/ext2fs/ext2_vfsops.c b/sys/gnu/fs/ext2fs/ext2_vfsops.c
index 90536828299a..1865dbb187a9 100644
--- a/sys/gnu/fs/ext2fs/ext2_vfsops.c
+++ b/sys/gnu/fs/ext2fs/ext2_vfsops.c
@@ -107,6 +107,8 @@ VFS_SET(ext2fs_vfsops, ext2fs, 0);
 
 static int ext2fs_inode_hash_lock;
 
+static int	ext2_check_sb_compat __P((struct ext2_super_block *es,
+					  dev_t dev, int ronly));
 static int	compute_sb_data __P((struct vnode * devvp,
 				     struct ext2_super_block * es,
 				     struct ext2_sb_info * fs));
@@ -365,6 +367,36 @@ static int ext2_check_descriptors (struct ext2_sb_info * sb)
         return 1;
 }
 
+static int
+ext2_check_sb_compat(es, dev, ronly)
+	struct ext2_super_block *es;
+	dev_t dev;
+	int ronly;
+{
+
+	if (es->s_magic != EXT2_SUPER_MAGIC) {
+		printf("ext2fs: %s: wrong magic number %#x (expected %#x)\n",
+		    devtoname(dev), es->s_magic, EXT2_SUPER_MAGIC);
+		return (1);
+	}
+	if (es->s_rev_level > EXT2_GOOD_OLD_REV) {
+		if (es->s_feature_incompat & ~EXT2_FEATURE_INCOMPAT_SUPP) {
+			printf(
+"WARNING: mount of %s denied due to unsupported optional features\n",
+			    devtoname(dev));
+			return (1);
+		}
+		if (!ronly &&
+		    (es->s_feature_ro_compat & ~EXT2_FEATURE_RO_COMPAT_SUPP)) {
+			printf(
+"WARNING: R/W mount of %s denied due to unsupported optional features\n",
+			    devtoname(dev));
+			return (1);
+		}
+	}
+	return (0);
+}
+
 /*
  * this computes the fields of the  ext2_sb_info structure from the
  * data in the ext2_super_block structure read in
@@ -506,14 +538,7 @@ ext2_reload(mountp, cred, p)
 	if ((error = bread(devvp, SBLOCK, SBSIZE, NOCRED, &bp)) != 0)
 		return (error);
 	es = (struct ext2_super_block *)bp->b_data;
-	if (es->s_magic != EXT2_SUPER_MAGIC) {
-		if(es->s_magic == EXT2_PRE_02B_MAGIC)
-		    printf("This filesystem bears the magic number of a pre "
-			   "0.2b version of ext2. This is not supported by "
-			   "Lites.\n");
-		else
-		    printf("Wrong magic number: %x (expected %x for ext2 fs\n",
-			es->s_magic, EXT2_SUPER_MAGIC);
+	if (ext2_check_sb_compat(es, devvp->v_rdev, 0) != 0) {
 		brelse(bp);
 		return (EIO);		/* XXX needs translation */
 	}
@@ -629,14 +654,7 @@ ext2_mountfs(devvp, mp, p)
 	if ((error = bread(devvp, SBLOCK, SBSIZE, NOCRED, &bp)) != 0)
 		goto out;
 	es = (struct ext2_super_block *)bp->b_data;
-	if (es->s_magic != EXT2_SUPER_MAGIC) {
-		if(es->s_magic == EXT2_PRE_02B_MAGIC)
-		    printf("This filesystem bears the magic number of a pre "
-			   "0.2b version of ext2. This is not supported by "
-			   "Lites.\n");
-		else
-		    printf("Wrong magic number: %x (expected %x for EXT2FS)\n",
-			es->s_magic, EXT2_SUPER_MAGIC);
+	if (ext2_check_sb_compat(es, dev, ronly) != 0) {
 		error = EINVAL;		/* XXX needs translation */
 		goto out;
 	}