diff --git a/libc/thread/sem_destroy.c b/libc/thread/sem_destroy.c
index fb0e3c3562b..053295c1b91 100644
--- a/libc/thread/sem_destroy.c
+++ b/libc/thread/sem_destroy.c
@@ -18,6 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/assert.h"
 #include "libc/intrin/atomic.h"
+#include "libc/intrin/strace.h"
 #include "libc/limits.h"
 #include "libc/sysv/errfuns.h"
 #include "libc/thread/semaphore.h"
@@ -40,14 +41,20 @@
  * @raise EBUSY if `sem` has waiters
  */
 int sem_destroy(sem_t *sem) {
-  int waiters;
+  int rc, waiters;
   npassert(sem->sem_magic != SEM_MAGIC_NAMED);
-  if (sem->sem_magic != SEM_MAGIC_UNNAMED)
-    return einval();
-  waiters = atomic_load_explicit(&sem->sem_waiters, memory_order_relaxed);
-  unassert(waiters >= 0);
-  if (waiters)
-    return ebusy();
-  atomic_store_explicit(&sem->sem_value, INT_MIN, memory_order_relaxed);
-  return 0;
+  if (sem->sem_magic != SEM_MAGIC_UNNAMED) {
+    rc = einval();
+  } else {
+    waiters = atomic_load_explicit(&sem->sem_waiters, memory_order_relaxed);
+    unassert(waiters >= 0);
+    if (waiters) {
+      rc = ebusy();
+    } else {
+      atomic_store_explicit(&sem->sem_value, INT_MIN, memory_order_relaxed);
+      rc = 0;
+    }
+  }
+  STRACE("sem_destroy(%p) → %d% m", sem, rc);
+  return rc;
 }
diff --git a/libc/thread/sem_init.c b/libc/thread/sem_init.c
index e86f1831340..da976752c8f 100644
--- a/libc/thread/sem_init.c
+++ b/libc/thread/sem_init.c
@@ -19,6 +19,7 @@
 #include "libc/calls/calls.h"
 #include "libc/dce.h"
 #include "libc/intrin/atomic.h"
+#include "libc/intrin/strace.h"
 #include "libc/limits.h"
 #include "libc/sysv/errfuns.h"
 #include "libc/thread/semaphore.h"
@@ -37,12 +38,17 @@
  * @raise EINVAL if `value` exceeds `SEM_VALUE_MAX`
  */
 int sem_init(sem_t *sem, int pshared, unsigned value) {
-  if (value > SEM_VALUE_MAX)
-    return einval();
-  sem->sem_magic = SEM_MAGIC_UNNAMED;
-  atomic_store_explicit(&sem->sem_value, value, memory_order_relaxed);
-  sem->sem_pshared = !!pshared;
-  sem->sem_pid = getpid();
-  sem->sem_waiters = 0;
-  return 0;
+  int rc;
+  if (value > SEM_VALUE_MAX) {
+    rc = einval();
+  } else {
+    sem->sem_magic = SEM_MAGIC_UNNAMED;
+    atomic_store_explicit(&sem->sem_value, value, memory_order_relaxed);
+    sem->sem_pshared = !!pshared;
+    sem->sem_pid = getpid();
+    sem->sem_waiters = 0;
+    rc = 0;
+  }
+  STRACE("sem_init(%p, %hhhd, %u) → %d% m", sem, pshared, value, rc);
+  return rc;
 }
diff --git a/libc/thread/sem_post.c b/libc/thread/sem_post.c
index 83fab34099a..80c164c9e80 100644
--- a/libc/thread/sem_post.c
+++ b/libc/thread/sem_post.c
@@ -46,7 +46,7 @@ int sem_post(sem_t *sem) {
   old = atomic_fetch_add_explicit(&sem->sem_value, 1, memory_order_acq_rel);
   unassert(old > INT_MIN);
   if (old >= 0) {
-    wakeups = nsync_futex_wake_(&sem->sem_value, 1, true);
+    wakeups = nsync_futex_wake_(&sem->sem_value, 1, sem->sem_pshared);
     npassert(wakeups >= 0);
     rc = 0;
   } else {
diff --git a/libc/thread/sem_timedwait.c b/libc/thread/sem_timedwait.c
index 7ac0f3acc59..be046ce6e65 100644
--- a/libc/thread/sem_timedwait.c
+++ b/libc/thread/sem_timedwait.c
@@ -59,7 +59,7 @@ static void sem_timedwait_cleanup(void *arg) {
  * @cancelationpoint
  */
 int sem_timedwait(sem_t *sem, const struct timespec *abstime) {
-  int i, v, rc, e = errno;
+  int v, rc, e = errno;
 
 #if 0
   if (IsXnuSilicon() && sem->sem_magic == SEM_MAGIC_KERNEL) {
@@ -103,16 +103,13 @@ int sem_timedwait(sem_t *sem, const struct timespec *abstime) {
   }
 #endif
 
-  for (i = 0; i < 7; ++i) {
-    rc = sem_trywait(sem);
-    if (!rc) {
-      return rc;
-    } else if (errno == EAGAIN) {
-      errno = e;
-      sem_delay(i);
-    } else {
-      return rc;
-    }
+  rc = sem_trywait(sem);
+  if (!rc) {
+    return rc;
+  } else if (errno == EAGAIN) {
+    errno = e;
+  } else {
+    return rc;
   }
 
   BEGIN_CANCELATION_POINT;
@@ -122,7 +119,8 @@ int sem_timedwait(sem_t *sem, const struct timespec *abstime) {
 
   do {
     if (!(v = atomic_load_explicit(&sem->sem_value, memory_order_relaxed))) {
-      rc = nsync_futex_wait_(&sem->sem_value, v, true, CLOCK_REALTIME, abstime);
+      rc = nsync_futex_wait_(&sem->sem_value, v, sem->sem_pshared,
+                             CLOCK_REALTIME, abstime);
       if (rc == -EINTR || rc == -ECANCELED) {
         errno = -rc;
         rc = -1;
diff --git a/test/posix/unnamed_semaphore_test.c b/test/posix/unnamed_semaphore_test.c
new file mode 100644
index 00000000000..f406f82b307
--- /dev/null
+++ b/test/posix/unnamed_semaphore_test.c
@@ -0,0 +1,35 @@
+#include <pthread.h>
+#include <semaphore.h>
+
+#define THREADS    10
+#define ITERATIONS 100000
+
+int g_count;
+sem_t g_sem;
+
+void *worker(void *arg) {
+  for (int i = 0; i < ITERATIONS; ++i) {
+    if (sem_wait(&g_sem))
+      exit(6);
+    ++g_count;
+    if (sem_post(&g_sem))
+      exit(7);
+  }
+  return 0;
+}
+
+int main(int argc, char *argv[]) {
+  pthread_t th[THREADS];
+  if (sem_init(&g_sem, 0, 1))
+    return 1;
+  for (int i = 0; i < THREADS; ++i)
+    if (pthread_create(&th[i], 0, worker, 0))
+      return 2;
+  for (int i = 0; i < THREADS; ++i)
+    if (pthread_join(th[i], 0))
+      return 3;
+  if (g_count != THREADS * ITERATIONS)
+    return 4;
+  if (sem_destroy(&g_sem))
+    return 5;
+}