diff --git a/CHANGELOG.md b/CHANGELOG.md
index 69484bbff6..465ddb64a8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,8 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 ### Changed
 
 ### Fixed
+- Made `preadv` take immutable slice of IoVec.
+  ([#944](https://github.com/nix-rust/nix/pull/914))
 
 ### Removed
 
diff --git a/src/sys/uio.rs b/src/sys/uio.rs
index 305c2ad0c1..45860be5aa 100644
--- a/src/sys/uio.rs
+++ b/src/sys/uio.rs
@@ -51,7 +51,7 @@ pub fn pwritev(fd: RawFd, iov: &[IoVec<&[u8]>],
           target_os = "linux",
           target_os = "netbsd",
           target_os = "openbsd"))]
-pub fn preadv(fd: RawFd, iov: &mut [IoVec<&mut [u8]>],
+pub fn preadv(fd: RawFd, iov: &[IoVec<&mut [u8]>],
               offset: off_t) -> Result<usize> {
     let res = unsafe {
         libc::preadv(fd, iov.as_ptr() as *const libc::iovec, iov.len() as c_int, offset)
diff --git a/test/sys/test_uio.rs b/test/sys/test_uio.rs
index c6331f1d7b..9f56c810a1 100644
--- a/test/sys/test_uio.rs
+++ b/test/sys/test_uio.rs
@@ -182,9 +182,9 @@ fn test_preadv() {
 
     {
         // Borrow the buffers into IoVecs and preadv into them
-        let mut iovecs: Vec<_> = buffers.iter_mut().map(
+        let iovecs: Vec<_> = buffers.iter_mut().map(
             |buf| IoVec::from_mut_slice(&mut buf[..])).collect();
-        assert_eq!(Ok(100), preadv(file.as_raw_fd(), &mut iovecs, 100));
+        assert_eq!(Ok(100), preadv(file.as_raw_fd(), &iovecs, 100));
     }
 
     let all = buffers.concat();