diff --git a/src/header/unistd/mod.rs b/src/header/unistd/mod.rs
index 4859819457..d443509b6e 100644
--- a/src/header/unistd/mod.rs
+++ b/src/header/unistd/mod.rs
@@ -601,9 +601,9 @@ pub extern "C" fn setreuid(ruid: uid_t, euid: uid_t) -> c_int {
     Sys::setreuid(ruid, euid)
 }
 
-// #[no_mangle]
+#[no_mangle]
 pub extern "C" fn setsid() -> pid_t {
-    unimplemented!();
+    Sys::setsid()
 }
 
 #[no_mangle]
diff --git a/src/platform/linux/mod.rs b/src/platform/linux/mod.rs
index 8f973c25b7..722f238366 100644
--- a/src/platform/linux/mod.rs
+++ b/src/platform/linux/mod.rs
@@ -476,6 +476,10 @@ impl Pal for Sys {
         e(unsafe { syscall!(SETREUID, ruid, euid) }) as c_int
     }
 
+    fn setsid() -> c_int {
+        e(unsafe { syscall!(SETSID) }) as c_int
+    }
+
     fn symlink(path1: &CStr, path2: &CStr) -> c_int {
         e(unsafe { syscall!(SYMLINKAT, path1.as_ptr(), AT_FDCWD, path2.as_ptr()) }) as c_int
     }
diff --git a/src/platform/pal/mod.rs b/src/platform/pal/mod.rs
index 91f04b4cc9..c6bdc770a3 100644
--- a/src/platform/pal/mod.rs
+++ b/src/platform/pal/mod.rs
@@ -175,6 +175,8 @@ pub trait Pal {
 
     fn setreuid(ruid: uid_t, euid: uid_t) -> c_int;
 
+    fn setsid() -> c_int;
+
     fn symlink(path1: &CStr, path2: &CStr) -> c_int;
 
     fn sync() -> c_int;
diff --git a/src/platform/redox/mod.rs b/src/platform/redox/mod.rs
index c2575956ec..decf4fd350 100644
--- a/src/platform/redox/mod.rs
+++ b/src/platform/redox/mod.rs
@@ -807,6 +807,12 @@ impl Pal for Sys {
         -1
     }
 
+    fn setsid() -> c_int {
+        // TODO
+        unsafe { errno = ENOSYS };
+        -1
+    }
+
     fn setregid(rgid: gid_t, egid: gid_t) -> c_int {
         e(syscall::setregid(rgid as usize, egid as usize)) as c_int
     }