diff --git a/libc/bionic/semaphore.cpp b/libc/bionic/semaphore.cpp
index ff84443..79b5d63 100644
--- a/libc/bionic/semaphore.cpp
+++ b/libc/bionic/semaphore.cpp
@@ -220,7 +220,7 @@
       return 0;
     }
 
-    __futex_wait_ex(sem_count_ptr, shared, shared | SEMCOUNT_MINUS_ONE, NULL);
+    __futex_wait_ex(sem_count_ptr, shared, shared | SEMCOUNT_MINUS_ONE, false, nullptr);
   }
 }
 
@@ -235,36 +235,29 @@
   }
 
   // Check it as per POSIX.
-  if (abs_timeout == NULL || abs_timeout->tv_sec < 0 || abs_timeout->tv_nsec < 0 || abs_timeout->tv_nsec >= NS_PER_S) {
-    errno = EINVAL;
+  int result = check_timespec(abs_timeout);
+  if (result != 0) {
+    errno = result;
     return -1;
   }
 
   unsigned int shared = SEM_GET_SHARED(sem_count_ptr);
 
   while (true) {
-    // POSIX mandates CLOCK_REALTIME here.
-    timespec ts;
-    if (!timespec_from_absolute_timespec(ts, *abs_timeout, CLOCK_REALTIME)) {
-      errno = ETIMEDOUT;
-      return -1;
-    }
-
     // Try to grab the semaphore. If the value was 0, this will also change it to -1.
     if (__sem_dec(sem_count_ptr) > 0) {
-      break;
+      return 0;
     }
 
     // Contention detected. Wait for a wakeup event.
-    int ret = __futex_wait_ex(sem_count_ptr, shared, shared | SEMCOUNT_MINUS_ONE, &ts);
+    int result = __futex_wait_ex(sem_count_ptr, shared, shared | SEMCOUNT_MINUS_ONE, true, abs_timeout);
 
     // Return in case of timeout or interrupt.
-    if (ret == -ETIMEDOUT || ret == -EINTR) {
-      errno = -ret;
+    if (result == -ETIMEDOUT || result == -EINTR) {
+      errno = -result;
       return -1;
     }
   }
-  return 0;
 }
 
 int sem_post(sem_t* sem) {