diff --git a/thread.c b/thread.c
index 48814ca51a..75d31cfb7a 100644
--- a/thread.c
+++ b/thread.c
@@ -106,6 +106,7 @@ static int rb_threadptr_pending_interrupt_empty_p(const rb_thread_t *th);
 static const char *thread_status_name(rb_thread_t *th, int detail);
 static void timespec_add(struct timespec *, const struct timespec *);
 static void timespec_sub(struct timespec *, const struct timespec *);
+static int timespec_cmp(const struct timespec *a, const struct timespec *b);
 static int timespec_update_expire(struct timespec *, const struct timespec *);
 static void getclockofday(struct timespec *);
 NORETURN(static void async_bug_fd(const char *mesg, int errno_arg, int fd));
diff --git a/thread_pthread.c b/thread_pthread.c
index c1cfe531f0..8f63da2e93 100644
--- a/thread_pthread.c
+++ b/thread_pthread.c
@@ -1613,11 +1613,45 @@ rb_sigwait_sleep(rb_thread_t *th, int sigwait_fd, const struct timespec *ts)
 {
     struct pollfd pfd;
 
-    pfd.fd = sigwait_fd;
-    pfd.events = POLLIN;
+    if (ubf_threads_empty()) {
+        pfd.fd = sigwait_fd;
+        pfd.events = POLLIN;
+        (void)ppoll(&pfd, 1, ts, 0);
+        check_signals_nogvl(th, sigwait_fd);
+    }
+    else {
+        static const struct timespec quantum = { 0, TIME_QUANTUM_USEC * 1000 };
+        struct timespec *endp = 0, end, now;
 
-    (void)ppoll(&pfd, 1, ts, 0);
-    check_signals_nogvl(th, sigwait_fd);
+        if (ts) {
+            getclockofday(&end);
+            timespec_add(&end, ts);
+            endp = &end;
+        }
+
+        getclockofday(&now);
+        for (;;) {
+            const struct timespec *tsp = &quantum;
+            struct timespec diff;
+            int n;
+
+            if (endp) {
+                diff = *endp;
+                timespec_sub(&diff, &now);
+                if (timespec_cmp(&diff, tsp) < 0)
+                    tsp = &diff;
+            }
+
+            n = ppoll(&pfd, 1, tsp, 0);
+            check_signals_nogvl(th, sigwait_fd);
+            if (RUBY_VM_INTERRUPTED(th->ec) || n != 0) break;
+
+            if (endp) {
+                getclockofday(&now);
+                if (timespec_cmp(&now, endp) >= 0) break;
+            }
+        }
+    }
 }
 
 static void