diff --git a/nptl/Makefile b/nptl/Makefile
index 60890b0ae2..4b83ed2532 100644
--- a/nptl/Makefile
+++ b/nptl/Makefile
@@ -312,6 +312,7 @@ tests = \
   tst-mutexpi10 \
   tst-mutexpi11 \
   tst-mutexpi12 \
+  tst-mutexpp11 \
   tst-once5 \
   tst-pthread-affinity-inheritance \
   tst-pthread-attr-affinity \
diff --git a/nptl/tst-mutexpp11.c b/nptl/tst-mutexpp11.c
new file mode 100644
index 0000000000..107a66209a
--- /dev/null
+++ b/nptl/tst-mutexpp11.c
@@ -0,0 +1,139 @@
+/* Test that PP mutex timedlock timeout restores thread priority (bug 34546).
+   Copyright (C) 2026 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <pthread.h>
+#include <support/check.h>
+#include <support/timespec.h>
+#include <support/xthread.h>
+#include <support/xtime.h>
+
+#include "tst-tpp.h"
+
+static pthread_mutex_t pp_mutex;
+static pthread_barrier_t barrier;
+
+static void *
+blocker_thread (void *ignored)
+{
+  xpthread_mutex_lock (&pp_mutex);
+
+  /* Tell the main thread that the mutex is held.  */
+  xpthread_barrier_wait (&barrier);
+
+  /* Wait for the main thread to finish its test.  */
+  xpthread_barrier_wait (&barrier);
+
+  xpthread_mutex_unlock (&pp_mutex);
+  return NULL;
+}
+
+/* Used by CHECK_TPP_PRIORITY.  */
+static int ret;
+
+static void
+test_timedlock (void)
+{
+  pthread_t thr = xpthread_create (NULL, blocker_thread, NULL);
+  xpthread_barrier_wait (&barrier);
+
+  CHECK_TPP_PRIORITY (4, 4);
+
+  /* Already-expired timeout.  */
+  static const struct timespec t = { -1, 0 };
+  TEST_COMPARE (pthread_mutex_timedlock (&pp_mutex, &t), ETIMEDOUT);
+
+  /* The timeout error path must restore the thread priority.  */
+  CHECK_TPP_PRIORITY (4, 4);
+
+  xpthread_barrier_wait (&barrier);
+  xpthread_join (thr);
+}
+
+static void
+test_clocklock (void)
+{
+  pthread_t thr = xpthread_create (NULL, blocker_thread, NULL);
+  xpthread_barrier_wait (&barrier);
+
+  CHECK_TPP_PRIORITY (4, 4);
+
+  /* Already-expired timeout, using CLOCK_REALTIME.  */
+  static const struct timespec t = { -1, 0 };
+  TEST_COMPARE (pthread_mutex_clocklock (&pp_mutex, CLOCK_REALTIME, &t),
+                ETIMEDOUT);
+
+  CHECK_TPP_PRIORITY (4, 4);
+
+  /* Already-expired timeout, using CLOCK_MONOTONIC.  */
+  TEST_COMPARE (pthread_mutex_clocklock (&pp_mutex, CLOCK_MONOTONIC, &t),
+                ETIMEDOUT);
+
+  CHECK_TPP_PRIORITY (4, 4);
+
+  xpthread_barrier_wait (&barrier);
+  xpthread_join (thr);
+}
+
+static void
+test_timedlock_late (void)
+{
+  pthread_t thr = xpthread_create (NULL, blocker_thread, NULL);
+  xpthread_barrier_wait (&barrier);
+
+  CHECK_TPP_PRIORITY (4, 4);
+
+  /* Timeout in the near future: blocks in the kernel before timing out.  */
+  struct timespec t;
+  xclock_gettime (CLOCK_REALTIME, &t);
+  t = timespec_add (t, make_timespec (0, 50 * 1000 * 1000));
+  TEST_COMPARE (pthread_mutex_timedlock (&pp_mutex, &t), ETIMEDOUT);
+
+  CHECK_TPP_PRIORITY (4, 4);
+
+  xpthread_barrier_wait (&barrier);
+  xpthread_join (thr);
+}
+
+static int
+do_test (void)
+{
+  init_tpp_test ();
+
+  /* Create the PP mutex.  */
+  {
+    pthread_mutexattr_t ma;
+    xpthread_mutexattr_init (&ma);
+    xpthread_mutexattr_setprotocol (&ma, PTHREAD_PRIO_PROTECT);
+    TEST_COMPARE (pthread_mutexattr_setprioceiling (&ma, 6), 0);
+    xpthread_mutex_init (&pp_mutex, &ma);
+    xpthread_mutexattr_destroy (&ma);
+  }
+
+  xpthread_barrier_init (&barrier, NULL, 2);
+  test_timedlock ();
+  test_clocklock ();
+  test_timedlock_late ();
+  xpthread_barrier_destroy (&barrier);
+
+  xpthread_mutex_destroy (&pp_mutex);
+
+  return ret;
+}
+
+#include <support/test-driver.c>