diff --git a/src/unix/mod.rs b/src/unix/mod.rs
index 364ff5590dcf257da8aed112844f0854dfc31fce..1084d9aa9537aa16216f0ecf8fe9949e35706dad 100644
--- a/src/unix/mod.rs
+++ b/src/unix/mod.rs
@@ -525,6 +525,7 @@ extern "C" {
     pub fn strspn(cs: *const c_char, ct: *const c_char) -> size_t;
     pub fn strcspn(cs: *const c_char, ct: *const c_char) -> size_t;
     pub fn strdup(cs: *const c_char) -> *mut c_char;
+    pub fn strndup(cs: *const c_char, n: size_t) -> *mut c_char;
     pub fn strpbrk(cs: *const c_char, ct: *const c_char) -> *mut c_char;
     pub fn strstr(cs: *const c_char, ct: *const c_char) -> *mut c_char;
     pub fn strcasecmp(s1: *const c_char, s2: *const c_char) -> c_int;