diff --git a/src/header/semaphore/cbindgen.toml b/src/header/semaphore/cbindgen.toml
index 213064b7ac..1eb7ba4cbf 100644
--- a/src/header/semaphore/cbindgen.toml
+++ b/src/header/semaphore/cbindgen.toml
@@ -1,4 +1,4 @@
-sys_includes = []
+sys_includes = ["time.h"]
 include_guard = "_RELIBC_SEMAPHORE_H"
 language = "C"
 style = "Type"
diff --git a/src/header/semaphore/mod.rs b/src/header/semaphore/mod.rs
index 34e4d1fcfb..2565beea6d 100644
--- a/src/header/semaphore/mod.rs
+++ b/src/header/semaphore/mod.rs
@@ -2,7 +2,10 @@
 //!
 //! See <https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/semaphore.h.html>.
 
-use crate::platform::types::*;
+use crate::{
+    header::time::{timespec, CLOCK_MONOTONIC, CLOCK_REALTIME},
+    platform::types::*,
+};
 
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/semaphore.h.html>.
 // TODO: Statically verify size and align
@@ -78,7 +81,27 @@ pub unsafe extern "C" fn sem_unlink(name: *const c_char) -> c_int {
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/sem_trywait.html>.
 #[no_mangle]
 pub unsafe extern "C" fn sem_wait(sem: *mut sem_t) -> c_int {
-    get(sem).wait(None);
+    get(sem).wait(None, CLOCK_MONOTONIC);
+
+    0
+}
+
+/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/sem_clockwait.html>.
+#[no_mangle]
+pub unsafe extern "C" fn sem_clockwait(
+    sem: *mut sem_t,
+    clock_id: clockid_t,
+    abstime: *const timespec,
+) -> c_int {
+    get(sem).wait(Some(&*abstime), clock_id);
+
+    0
+}
+
+/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/sem_timedwait.html>.
+#[no_mangle]
+pub unsafe extern "C" fn sem_timedwait(sem: *mut sem_t, abstime: *const timespec) -> c_int {
+    get(sem).wait(Some(&*abstime), CLOCK_REALTIME);
 
     0
 }
diff --git a/src/sync/semaphore.rs b/src/sync/semaphore.rs
index 34a1283b05..eee6ba90b6 100644
--- a/src/sync/semaphore.rs
+++ b/src/sync/semaphore.rs
@@ -51,7 +51,7 @@ impl Semaphore {
         }
     }
 
-    pub fn wait(&self, timeout_opt: Option<&timespec>) -> Result<(), ()> {
+    pub fn wait(&self, timeout_opt: Option<&timespec>, clock_id: clockid_t) -> Result<(), ()> {
         loop {
             let value = self.try_wait();
 
@@ -61,7 +61,7 @@ impl Semaphore {
 
             if let Some(timeout) = timeout_opt {
                 let mut time = timespec::default();
-                unsafe { clock_gettime(CLOCK_MONOTONIC, &mut time) };
+                unsafe { clock_gettime(clock_id, &mut time) };
                 if (time.tv_sec > timeout.tv_sec)
                     || (time.tv_sec == timeout.tv_sec && time.tv_nsec >= timeout.tv_nsec)
                 {