diff --git a/fs/ecryptfs/main.c b/fs/ecryptfs/main.c
index 7d3ed6bfcfa55d16c6cb9764aaded383a6a5fff7..cbd4e18adb204438d45b865469d38b7af97a9904 100644
--- a/fs/ecryptfs/main.c
+++ b/fs/ecryptfs/main.c
@@ -483,6 +483,7 @@ static int ecryptfs_parse_options(struct ecryptfs_sb_info *sbi, char *options)
 }
 
 struct kmem_cache *ecryptfs_sb_info_cache;
+static struct file_system_type ecryptfs_fs_type;
 
 /**
  * ecryptfs_read_super
@@ -503,6 +504,13 @@ static int ecryptfs_read_super(struct super_block *sb, const char *dev_name)
 		ecryptfs_printk(KERN_WARNING, "path_lookup() failed\n");
 		goto out;
 	}
+	if (path.dentry->d_sb->s_type == &ecryptfs_fs_type) {
+		rc = -EINVAL;
+		printk(KERN_ERR "Mount on filesystem of type "
+			"eCryptfs explicitly disallowed due to "
+			"known incompatibilities\n");
+		goto out_free;
+	}
 	ecryptfs_set_superblock_lower(sb, path.dentry->d_sb);
 	sb->s_maxbytes = path.dentry->d_sb->s_maxbytes;
 	sb->s_blocksize = path.dentry->d_sb->s_blocksize;