diff --git a/tests/pthread_test.cpp b/tests/pthread_test.cpp
index 9ecb10c..f812df5 100644
--- a/tests/pthread_test.cpp
+++ b/tests/pthread_test.cpp
@@ -356,9 +356,9 @@
 }
 
 static void* SignalHandlerFn(void* arg) {
-  sigset_t wait_set;
-  sigfillset(&wait_set);
-  return reinterpret_cast<void*>(sigwait(&wait_set, reinterpret_cast<int*>(arg)));
+  sigset64_t wait_set;
+  sigfillset64(&wait_set);
+  return reinterpret_cast<void*>(sigwait64(&wait_set, reinterpret_cast<int*>(arg)));
 }
 
 TEST(pthread, pthread_sigmask) {
@@ -402,6 +402,47 @@
   ASSERT_EQ(0, pthread_sigmask(SIG_SETMASK, &original_set, NULL));
 }
 
+TEST(pthread, pthread_sigmask64_SIGTRMIN) {
+  // Check that SIGRTMIN isn't blocked.
+  sigset64_t original_set;
+  sigemptyset64(&original_set);
+  ASSERT_EQ(0, pthread_sigmask64(SIG_BLOCK, NULL, &original_set));
+  ASSERT_FALSE(sigismember64(&original_set, SIGRTMIN));
+
+  // Block SIGRTMIN.
+  sigset64_t set;
+  sigemptyset64(&set);
+  sigaddset64(&set, SIGRTMIN);
+  ASSERT_EQ(0, pthread_sigmask64(SIG_BLOCK, &set, NULL));
+
+  // Check that SIGRTMIN is blocked.
+  sigset64_t final_set;
+  sigemptyset64(&final_set);
+  ASSERT_EQ(0, pthread_sigmask64(SIG_BLOCK, NULL, &final_set));
+  ASSERT_TRUE(sigismember64(&final_set, SIGRTMIN));
+  // ...and that sigprocmask64 agrees with pthread_sigmask64.
+  sigemptyset64(&final_set);
+  ASSERT_EQ(0, sigprocmask64(SIG_BLOCK, NULL, &final_set));
+  ASSERT_TRUE(sigismember64(&final_set, SIGRTMIN));
+
+  // Spawn a thread that calls sigwait64 and tells us what it received.
+  pthread_t signal_thread;
+  int received_signal = -1;
+  ASSERT_EQ(0, pthread_create(&signal_thread, NULL, SignalHandlerFn, &received_signal));
+
+  // Send that thread SIGRTMIN.
+  pthread_kill(signal_thread, SIGRTMIN);
+
+  // See what it got.
+  void* join_result;
+  ASSERT_EQ(0, pthread_join(signal_thread, &join_result));
+  ASSERT_EQ(SIGRTMIN, received_signal);
+  ASSERT_EQ(0U, reinterpret_cast<uintptr_t>(join_result));
+
+  // Restore the original signal mask.
+  ASSERT_EQ(0, pthread_sigmask64(SIG_SETMASK, &original_set, NULL));
+}
+
 static void test_pthread_setname_np__pthread_getname_np(pthread_t t) {
   ASSERT_EQ(0, pthread_setname_np(t, "short"));
   char name[32];