diff --git a/wasi-filesystem.wit.md b/wasi-filesystem.wit.md
index d19ef6f..bd3b126 100644
--- a/wasi-filesystem.wit.md
+++ b/wasi-filesystem.wit.md
@@ -96,10 +96,6 @@ flags descriptor-flags {
 /// 
 /// Note: This was called `filestat` in earlier versions of WASI.
 record descriptor-stat {
-    /// Device ID of device containing the file.
-    dev: device,
-    /// File serial number.
-    ino: inode,
     /// File type.
     %type: descriptor-type,
     /// Number of hard links to the file.
@@ -162,19 +158,6 @@ flags mode {
 type linkcount = u64
 ```
 
-## `device`
-```wit
-/// Identifier for a device containing a file system. Can be used in combination
-/// with `inode` to uniquely identify a file or directory in the filesystem.
-type device = u64
-```
-
-## `inode`
-```wit
-/// Filesystem object serial number that is unique within its file system.
-type inode = u64
-```
-
 ## `new-timestamp`
 ```wit
 /// When setting a timestamp, this gives the value to set it to.
@@ -193,14 +176,6 @@ variant new-timestamp {
 ```wit
 /// A directory entry. 
 record dir-entry {
-    /// The serial number of the object referred to by this directory entry.
-    /// May be none if the inode value is not known.
-    ///
-    /// When this is none, libc implementations might do an extra `stat-at`
-    /// call to retrieve the inode number to fill their `d_ino` fields, so
-    /// implementations which can set this to a non-none value should do so.
-    ino: option<inode>,
-
     /// The type of the file referred to by this directory entry.
     %type: descriptor-type,
 
@@ -861,6 +836,28 @@ try-lock-exclusive: func() -> result<_, errno>
 unlock: func() -> result<_, errno>
 ```
 
+## `is-same-file`
+```wit
+/// Test whether two descriptors refer to the same file or directory.
+///
+/// In POSIX, this corresponds to testing whether the two descriptors have the
+/// same device (`st_dev`) and inode (`st_ino` or `d_ino`) numbers.
+/// wasi-filesystem does not expose device and inode numbers, so this function
+/// may be used instead.
+is-same-file: func(other: descriptor) -> bool
+
+/// Test whether two descriptors refer to files or directories on the same
+/// mountpoint.
+///
+/// `rename-at` only works when source and destination are on the same mount
+/// point. This function provides a way of testing whether two files or
+/// directories are on the same mount point.
+///
+/// In POSIX, this corresponds to testing whether the two descriptors have the
+/// same device (`st_dev`) number. wasi-filesystem does not expose device
+/// numbers, so this function may be used instead.
+is-same-mountpoint(other: descriptor) -> bool
+
 ```wit
 }
 ```