diff --git a/src/unix/core.c b/src/unix/core.c
index 10f6f70bd..6f284ffa7 100644
--- a/src/unix/core.c
+++ b/src/unix/core.c
@@ -74,7 +74,7 @@
 #include <sys/ioctl.h>
 #endif
 
-static void uv__run_pending(uv_loop_t* loop);
+static int uv__run_pending(uv_loop_t* loop);
 
 /* Verify that uv_buf_t is ABI-compatible with struct iovec. */
 STATIC_ASSERT(sizeof(uv_buf_t) == sizeof(struct iovec));
@@ -304,6 +304,7 @@ int uv_loop_alive(const uv_loop_t* loop) {
 int uv_run(uv_loop_t* loop, uv_run_mode mode) {
   int timeout;
   int r;
+  int ran_pending;
 
   r = uv__loop_alive(loop);
   if (!r)
@@ -312,12 +313,12 @@ int uv_run(uv_loop_t* loop, uv_run_mode mode) {
   while (r != 0 && loop->stop_flag == 0) {
     uv__update_time(loop);
     uv__run_timers(loop);
-    uv__run_pending(loop);
+    ran_pending = uv__run_pending(loop);
     uv__run_idle(loop);
     uv__run_prepare(loop);
 
     timeout = 0;
-    if (mode != UV_RUN_NOWAIT)
+    if ((mode == UV_RUN_ONCE && !ran_pending) || mode == UV_RUN_DEFAULT)
       timeout = uv_backend_timeout(loop);
 
     uv__io_poll(loop, timeout);
@@ -693,10 +694,13 @@ int uv_fileno(const uv_handle_t* handle, uv_os_fd_t* fd) {
 }
 
 
-static void uv__run_pending(uv_loop_t* loop) {
+static int uv__run_pending(uv_loop_t* loop) {
   QUEUE* q;
   uv__io_t* w;
 
+  if (QUEUE_EMPTY(&loop->pending_queue))
+    return 0;
+
   while (!QUEUE_EMPTY(&loop->pending_queue)) {
     q = QUEUE_HEAD(&loop->pending_queue);
     QUEUE_REMOVE(q);
@@ -705,6 +709,8 @@ static void uv__run_pending(uv_loop_t* loop) {
     w = QUEUE_DATA(q, uv__io_t, pending_queue);
     w->cb(loop, w, UV__POLLOUT);
   }
+
+  return 1;
 }
 
 
diff --git a/src/win/core.c b/src/win/core.c
index 23d6561ce..2bef8b7f3 100644
--- a/src/win/core.c
+++ b/src/win/core.c
@@ -387,6 +387,7 @@ int uv_loop_alive(const uv_loop_t* loop) {
 int uv_run(uv_loop_t *loop, uv_run_mode mode) {
   DWORD timeout;
   int r;
+  int ran_pending;
   void (*poll)(uv_loop_t* loop, DWORD timeout);
 
   if (pGetQueuedCompletionStatusEx)
@@ -402,12 +403,12 @@ int uv_run(uv_loop_t *loop, uv_run_mode mode) {
     uv_update_time(loop);
     uv_process_timers(loop);
 
-    uv_process_reqs(loop);
+    ran_pending = uv_process_reqs(loop);
     uv_idle_invoke(loop);
     uv_prepare_invoke(loop);
 
     timeout = 0;
-    if (mode != UV_RUN_NOWAIT)
+    if ((mode == UV_RUN_ONCE && !ran_pending) || mode == UV_RUN_DEFAULT)
       timeout = uv_backend_timeout(loop);
 
     (*poll)(loop, timeout);
diff --git a/src/win/req-inl.h b/src/win/req-inl.h
index 97342e5c7..46c7d9b10 100644
--- a/src/win/req-inl.h
+++ b/src/win/req-inl.h
@@ -130,14 +130,13 @@ INLINE static void uv_insert_pending_req(uv_loop_t* loop, uv_req_t* req) {
   } while (0)
 
 
-INLINE static void uv_process_reqs(uv_loop_t* loop) {
+INLINE static int uv_process_reqs(uv_loop_t* loop) {
   uv_req_t* req;
   uv_req_t* first;
   uv_req_t* next;
 
-  if (loop->pending_reqs_tail == NULL) {
-    return;
-  }
+  if (loop->pending_reqs_tail == NULL)
+    return 0;
 
   first = loop->pending_reqs_tail->next_req;
   next = first;
@@ -207,6 +206,8 @@ INLINE static void uv_process_reqs(uv_loop_t* loop) {
         assert(0);
     }
   }
+
+  return 1;
 }
 
 #endif /* UV_WIN_REQ_INL_H_ */