diff --git a/src/unix/bsd/freebsdlike/mod.rs b/src/unix/bsd/freebsdlike/mod.rs
index ebcdee7c..8481e0cf 100644
--- a/src/unix/bsd/freebsdlike/mod.rs
+++ b/src/unix/bsd/freebsdlike/mod.rs
@@ -575,6 +575,7 @@ extern {
                            len: ::off_t) -> ::c_int;
     pub fn sched_setscheduler(pid: ::pid_t, policy: ::c_int, param: *const sched_param) -> ::c_int;
     pub fn sched_getscheduler(pid: ::pid_t) -> ::c_int;
+    pub fn memrchr(cx: *const ::c_void, c: ::c_int, n: ::size_t) -> *mut ::c_void;
 }
 
 cfg_if! {
diff --git a/src/unix/bsd/openbsdlike/mod.rs b/src/unix/bsd/openbsdlike/mod.rs
index 17a90ee6..3d43e526 100644
--- a/src/unix/bsd/openbsdlike/mod.rs
+++ b/src/unix/bsd/openbsdlike/mod.rs
@@ -363,6 +363,7 @@ extern {
     pub fn pthread_set_name_np(tid: ::pthread_t, name: *const ::c_char);
     pub fn pthread_stackseg_np(thread: ::pthread_t,
                                sinfo: *mut ::stack_t) -> ::c_uint;
+    pub fn memrchr(cx: *const ::c_void, c: ::c_int, n: ::size_t) -> *mut ::c_void;
 }
 
 cfg_if! {
diff --git a/src/unix/notbsd/mod.rs b/src/unix/notbsd/mod.rs
index 7666fcc9..046fbe38 100644
--- a/src/unix/notbsd/mod.rs
+++ b/src/unix/notbsd/mod.rs
@@ -606,6 +606,7 @@ extern {
                  arg: *mut ::c_void, ...) -> ::c_int;
     pub fn statfs(path: *const ::c_char, buf: *mut statfs) -> ::c_int;
     pub fn fstatfs(fd: ::c_int, buf: *mut statfs) -> ::c_int;
+    pub fn memrchr(cx: *const ::c_void, c: ::c_int, n: ::size_t) -> *mut ::c_void;
 }
 
 cfg_if! {