diff --git a/src/unix/thread.c b/src/unix/thread.c
index aa637180..f85de1a4 100644
--- a/src/unix/thread.c
+++ b/src/unix/thread.c
@@ -170,7 +170,10 @@ void uv_once(uv_once_t* guard, void (*callback)(void)) {
 #if defined(__APPLE__) && defined(__MACH__)
 
 int uv_sem_init(uv_sem_t* sem, unsigned int value) {
-  return semaphore_create(mach_task_self(), sem, SYNC_POLICY_FIFO, value);
+  if (semaphore_create(mach_task_self(), sem, SYNC_POLICY_FIFO, value))
+    return -1;
+  else
+    return 0;
 }