diff --git a/README.md b/README.md
index 97ca145f1a..72f7486d2e 100644
--- a/README.md
+++ b/README.md
@@ -46,46 +46,59 @@ limitations. Support for platforms is split into three tiers:
 
 The following targets are supported by `nix`:
 
-Tier 1:
-  * aarch64-apple-darwin
-  * aarch64-unknown-linux-gnu
-  * arm-unknown-linux-gnueabi
-  * armv7-unknown-linux-gnueabihf
-  * i686-unknown-freebsd
-  * i686-unknown-linux-gnu
-  * i686-unknown-linux-musl
-  * mips-unknown-linux-gnu
-  * mips64-unknown-linux-gnuabi64
-  * mips64el-unknown-linux-gnuabi64
-  * mipsel-unknown-linux-gnu
-  * powerpc64le-unknown-linux-gnu
-  * x86_64-unknown-freebsd
-  * x86_64-unknown-linux-gnu
-  * x86_64-unknown-linux-musl
-
-Tier 2:
-  * aarch64-apple-ios
-  * aarch64-linux-android
-  * arm-linux-androideabi
-  * arm-unknown-linux-musleabi
-  * armv7-linux-androideabi
-  * i686-linux-android
-  * powerpc-unknown-linux-gnu
-  * s390x-unknown-linux-gnu
-  * x86_64-apple-ios
-  * x86_64-linux-android
-  * x86_64-apple-darwin
-  * x86_64-unknown-illumos
-  * x86_64-unknown-netbsd
-
-Tier 3:
-  * armv7-unknown-linux-uclibceabihf
-  * x86_64-fuchsia
-  * x86_64-unknown-dragonfly
-  * x86_64-unknown-haiku
-  * x86_64-unknown-linux-gnux32
-  * x86_64-unknown-openbsd
-  * x86_64-unknown-redox
+<table>
+ <tr>
+  <th>Tier 1</th>
+  <th>Tier 2</th>
+  <th>Tier 3</th>
+ </tr>
+ <tr>
+  <td>
+   <ul>
+    <li>aarch64-apple-darwin</li>
+    <li>aarch64-unknown-linux-gnu</li>
+    <li>arm-unknown-linux-gnueabi</li>
+    <li>armv7-unknown-linux-gnueabihf</li>
+    <li>i686-unknown-freebsd</li>
+    <li>i686-unknown-linux-gnu</li>
+    <li>i686-unknown-linux-musl</li>
+    <li>mips-unknown-linux-gnu</li>
+    <li>mips64-unknown-linux-gnuabi64</li>
+    <li>mips64el-unknown-linux-gnuabi64</li>
+    <li>mipsel-unknown-linux-gnu</li>
+    <li>powerpc64le-unknown-linux-gnu</li>
+    <li>x86_64-unknown-freebsd</li>
+    <li>x86_64-unknown-linux-gnu</li>
+    <li>x86_64-unknown-linux-musl</li>
+   </ul>
+  </td>
+  <td>
+   <ul>
+    <li>aarch64-apple-ios</li>
+    <li>aarch64-linux-android</li>
+    <li>arm-linux-androideabi</li>
+    <li>arm-unknown-linux-musleabi</li>
+    <li>armv7-linux-androideabi</li>
+    <li>i686-linux-android</li>
+    <li>powerpc-unknown-linux-gnu</li>
+    <li>s390x-unknown-linux-gnu</li>
+    <li>x86_64-apple-ios</li>
+    <li>x86_64-linux-android</li>
+    <li>x86_64-apple-darwin</li>
+    <li>x86_64-unknown-illumos</li>
+    <li>x86_64-unknown-netbsd</li>
+   </td>
+   <td>
+    <li>armv7-unknown-linux-uclibceabihf</li>
+    <li>x86_64-fuchsia</li>
+    <li>x86_64-unknown-dragonfly</li>
+    <li>x86_64-unknown-haiku</li>
+    <li>x86_64-unknown-linux-gnux32</li>
+    <li>x86_64-unknown-openbsd</li>
+    <li>x86_64-unknown-redox</li>
+   </td>
+  </tr>
+</table>
 
 ## Minimum Supported Rust Version (MSRV)
 
diff --git a/src/unistd.rs b/src/unistd.rs
index ae1cca9542..8cad67f4a4 100644
--- a/src/unistd.rs
+++ b/src/unistd.rs
@@ -35,6 +35,7 @@ use std::ffi::{CString, OsStr};
 use std::os::unix::ffi::OsStrExt;
 use std::os::unix::ffi::OsStringExt;
 use std::os::unix::io::RawFd;
+use std::os::unix::io::{AsFd, AsRawFd};
 use std::path::PathBuf;
 use std::{fmt, mem, ptr};
 
@@ -1255,8 +1256,8 @@ pub fn truncate<P: ?Sized + NixPath>(path: &P, len: off_t) -> Result<()> {
 ///
 /// See also
 /// [ftruncate(2)](https://pubs.opengroup.org/onlinepubs/9699919799/functions/ftruncate.html)
-pub fn ftruncate(fd: RawFd, len: off_t) -> Result<()> {
-    Errno::result(unsafe { libc::ftruncate(fd, len) }).map(drop)
+pub fn ftruncate<Fd: AsFd>(fd: Fd, len: off_t) -> Result<()> {
+    Errno::result(unsafe { libc::ftruncate(fd.as_fd().as_raw_fd(), len) }).map(drop)
 }
 
 pub fn isatty(fd: RawFd) -> Result<bool> {
diff --git a/test/test_unistd.rs b/test/test_unistd.rs
index 1d50c5fa48..10284e4127 100644
--- a/test/test_unistd.rs
+++ b/test/test_unistd.rs
@@ -772,15 +772,12 @@ fn test_ftruncate() {
     let tempdir = tempdir().unwrap();
     let path = tempdir.path().join("file");
 
-    let tmpfd = {
-        let mut tmp = File::create(&path).unwrap();
-        const CONTENTS: &[u8] = b"12345678";
-        tmp.write_all(CONTENTS).unwrap();
-        tmp.into_raw_fd()
-    };
+    let mut file = File::create(&path).unwrap();
+    const CONTENTS: &[u8] = b"12345678";
+    file.write_all(CONTENTS).unwrap();
 
-    ftruncate(tmpfd, 2).unwrap();
-    close(tmpfd).unwrap();
+    ftruncate(&file, 2).unwrap();
+    drop(file);
 
     let metadata = fs::metadata(&path).unwrap();
     assert_eq!(2, metadata.len());