diff --git a/include/uv-private/uv-win.h b/include/uv-private/uv-win.h
index 82c0cff1..574aa8f2 100644
--- a/include/uv-private/uv-win.h
+++ b/include/uv-private/uv-win.h
@@ -487,8 +487,8 @@ RB_HEAD(uv_timer_tree_s, uv_timer_s);
 
 #define UV_TIMER_PRIVATE_FIELDS                                               \
   RB_ENTRY(uv_timer_s) tree_entry;                                            \
-  int64_t due;                                                                \
-  int64_t repeat;                                                             \
+  uint64_t due;                                                               \
+  uint64_t repeat;                                                            \
   uint64_t start_id;                                                          \
   uv_timer_cb timer_cb;
 
diff --git a/include/uv.h b/include/uv.h
index e1eaf81e..453b90c4 100644
--- a/include/uv.h
+++ b/include/uv.h
@@ -1170,15 +1170,11 @@ UV_EXTERN int uv_timer_init(uv_loop_t*, uv_timer_t* handle);
  *
  * If repeat is non-zero, the callback fires first after timeout milliseconds
  * and then repeatedly after repeat milliseconds.
- *
- * timeout and repeat are signed integers but that will change in a future
- * version of libuv. Don't pass in negative values, you'll get a nasty surprise
- * when that change becomes effective.
  */
 UV_EXTERN int uv_timer_start(uv_timer_t* handle,
                              uv_timer_cb cb,
-                             int64_t timeout,
-                             int64_t repeat);
+                             uint64_t timeout,
+                             uint64_t repeat);
 
 UV_EXTERN int uv_timer_stop(uv_timer_t* handle);
 
@@ -1195,9 +1191,9 @@ UV_EXTERN int uv_timer_again(uv_timer_t* handle);
  * non-repeating before, it will have been stopped. If it was repeating, then
  * the old repeat value will have been used to schedule the next timeout.
  */
-UV_EXTERN void uv_timer_set_repeat(uv_timer_t* handle, int64_t repeat);
+UV_EXTERN void uv_timer_set_repeat(uv_timer_t* handle, uint64_t repeat);
 
-UV_EXTERN int64_t uv_timer_get_repeat(uv_timer_t* handle);
+UV_EXTERN uint64_t uv_timer_get_repeat(uv_timer_t* handle);
 
 
 /*
diff --git a/src/unix/timer.c b/src/unix/timer.c
index 2c2458d0..5c4208ec 100644
--- a/src/unix/timer.c
+++ b/src/unix/timer.c
@@ -52,11 +52,8 @@ int uv_timer_init(uv_loop_t* loop, uv_timer_t* handle) {
 
 int uv_timer_start(uv_timer_t* handle,
                    uv_timer_cb cb,
-                   int64_t timeout,
-                   int64_t repeat) {
-  assert(timeout >= 0);
-  assert(repeat >= 0);
-
+                   uint64_t timeout,
+                   uint64_t repeat) {
   if (uv__is_active(handle))
     uv_timer_stop(handle);
 
@@ -97,13 +94,12 @@ int uv_timer_again(uv_timer_t* handle) {
 }
 
 
-void uv_timer_set_repeat(uv_timer_t* handle, int64_t repeat) {
-  assert(repeat >= 0);
+void uv_timer_set_repeat(uv_timer_t* handle, uint64_t repeat) {
   handle->repeat = repeat;
 }
 
 
-int64_t uv_timer_get_repeat(uv_timer_t* handle) {
+uint64_t uv_timer_get_repeat(uv_timer_t* handle) {
   return handle->repeat;
 }
 
diff --git a/src/win/timer.c b/src/win/timer.c
index 3364f6c0..60991295 100644
--- a/src/win/timer.c
+++ b/src/win/timer.c
@@ -87,8 +87,8 @@ void uv_timer_endgame(uv_loop_t* loop, uv_timer_t* handle) {
 }
 
 
-int uv_timer_start(uv_timer_t* handle, uv_timer_cb timer_cb, int64_t timeout,
-    int64_t repeat) {
+int uv_timer_start(uv_timer_t* handle, uv_timer_cb timer_cb, uint64_t timeout,
+    uint64_t repeat) {
   uv_loop_t* loop = handle->loop;
   uv_timer_t* old;
 
@@ -157,13 +157,13 @@ int uv_timer_again(uv_timer_t* handle) {
 }
 
 
-void uv_timer_set_repeat(uv_timer_t* handle, int64_t repeat) {
+void uv_timer_set_repeat(uv_timer_t* handle, uint64_t repeat) {
   assert(handle->type == UV_TIMER);
   handle->repeat = repeat;
 }
 
 
-int64_t uv_timer_get_repeat(uv_timer_t* handle) {
+uint64_t uv_timer_get_repeat(uv_timer_t* handle) {
   assert(handle->type == UV_TIMER);
   return handle->repeat;
 }