diff --git a/system/lib/libc/musl/src/time/clock_nanosleep.c b/system/lib/libc/musl/src/time/clock_nanosleep.c
index 434fc4939e146..7ad2aba1a0b7a 100644
--- a/system/lib/libc/musl/src/time/clock_nanosleep.c
+++ b/system/lib/libc/musl/src/time/clock_nanosleep.c
@@ -16,7 +16,18 @@ int __clock_nanosleep(clockid_t clk, int flags, const struct timespec *req, stru
 	if (!req || req->tv_nsec < 0 || req->tv_nsec > 999999999L || req->tv_sec < 0) {
 		return EINVAL;
 	}
-	emscripten_thread_sleep(req->tv_sec * 1000.0 + req->tv_nsec / 1e6);
+	struct timespec sleep_for = *req;
+	if (flags & TIMER_ABSTIME) {
+		struct timespec now;
+		clock_gettime(clk, &now);
+		if (now.tv_sec > req->tv_sec || (now.tv_sec == req->tv_sec && now.tv_nsec >= req->tv_nsec)) {
+			// The requested time has already passed
+			return 0;
+		}
+		sleep_for.tv_sec = req->tv_sec - now.tv_sec;
+		sleep_for.tv_nsec = req->tv_nsec - now.tv_nsec;
+	}
+	emscripten_thread_sleep(sleep_for.tv_sec * 1000.0 + sleep_for.tv_nsec / 1e6);
 	return 0;
 #else
 #ifdef SYS_clock_nanosleep_time64
diff --git a/tests/other/test_clock_nanosleep.c b/tests/other/test_clock_nanosleep.c
new file mode 100644
index 0000000000000..a60efbe67120e
--- /dev/null
+++ b/tests/other/test_clock_nanosleep.c
@@ -0,0 +1,42 @@
+#include <assert.h>
+#include <stdio.h>
+#include <time.h>
+
+long long get_time_ms() {
+  struct timespec now;
+  clock_gettime(CLOCK_MONOTONIC, &now);
+  return (now.tv_sec * 1000) + (now.tv_nsec / 1000 / 1000);
+}
+
+int main(void) {
+  // Sleep for 10ms relative to current time (i.e. without TIMER_ABSTIME).
+  struct timespec sleep_for;
+  sleep_for.tv_sec = 0;
+  sleep_for.tv_nsec = 10 * 1000 * 1000;
+  long long before = get_time_ms();
+  printf("before: %lli\n", before);
+  clock_nanosleep(CLOCK_MONOTONIC, 0, &sleep_for, NULL);
+  long long after = get_time_ms();
+  printf("after: %lli\n", after);
+
+  // Check we slept at least 10ms
+  assert(after > before);
+  assert(after - before >= 10);
+  assert(after - before < 10000);
+
+  before = get_time_ms();
+  printf("before: %lli\n", before);
+  struct timespec deadline;
+  clock_gettime(CLOCK_MONOTONIC, &deadline);
+  deadline.tv_nsec += 20 * 1000 * 1000;
+  clock_nanosleep(CLOCK_MONOTONIC, TIMER_ABSTIME, &deadline, NULL);
+  after = get_time_ms();
+  printf("after: %lli\n", after);
+
+  // Check we slept at least 20ms
+  assert(after > before);
+  assert(after - before >= 20);
+  assert(after - before < 10000);
+
+  return 0;
+}
diff --git a/tests/test_other.py b/tests/test_other.py
index b39d52038ff76..f277c50d7be24 100644
--- a/tests/test_other.py
+++ b/tests/test_other.py
@@ -11806,3 +11806,6 @@ def test_wasm_worker_preprocessor_flags(self):
   def test_debug_opt_warning(self):
     err = self.expect_fail([EMCC, test_file('hello_world.c'), '-O2', '-g', '-Werror'])
     self.assertContained('error: running limited binaryen optimizations because DWARF info requested (or indirectly required) [-Wlimited-postlink-optimizations]', err)
+
+  def test_clock_nanosleep(self):
+    self.do_runf(test_file('other/test_clock_nanosleep.c'))