diff --git a/src/unix/bsd/freebsdlike/freebsd/mod.rs b/src/unix/bsd/freebsdlike/freebsd/mod.rs
index e7a312741cebc..a2a6d69375b66 100644
--- a/src/unix/bsd/freebsdlike/freebsd/mod.rs
+++ b/src/unix/bsd/freebsdlike/freebsd/mod.rs
@@ -881,6 +881,7 @@ extern {
     pub fn jail_set(iov: *mut ::iovec, niov: ::c_uint, flags: ::c_int)
                     -> ::c_int;
 
+    pub fn fdatasync(fd: ::c_int) -> ::c_int;
     pub fn posix_fallocate(fd: ::c_int, offset: ::off_t,
                            len: ::off_t) -> ::c_int;
     pub fn posix_fadvise(fd: ::c_int, offset: ::off_t, len: ::off_t,