diff --git a/Libraries/Core/Timers/JSTimers.js b/Libraries/Core/Timers/JSTimers.js
index 45129f1b91..6d8da69e86 100644
--- a/Libraries/Core/Timers/JSTimers.js
+++ b/Libraries/Core/Timers/JSTimers.js
@@ -244,11 +244,7 @@ const JSTimers = {
    * @param {function} func Callback to be invoked after `duration` ms.
    * @param {number} duration Number of milliseconds.
    */
-  setTimeout: function(
-    func: Function,
-    duration: number,
-    ...args?: any
-  ): number {
+  setTimeout: function(func: Function, duration: number, ...args: any): number {
     if (__DEV__ && IS_ANDROID && duration > MAX_TIMER_DURATION_MS) {
       console.warn(
         ANDROID_LONG_TIMER_MESSAGE +
@@ -273,7 +269,7 @@ const JSTimers = {
   setInterval: function(
     func: Function,
     duration: number,
-    ...args?: any
+    ...args: any
   ): number {
     if (__DEV__ && IS_ANDROID && duration > MAX_TIMER_DURATION_MS) {
       console.warn(
@@ -296,7 +292,7 @@ const JSTimers = {
    * @param {function} func Callback to be invoked before the end of the
    * current JavaScript execution loop.
    */
-  setImmediate: function(func: Function, ...args?: any) {
+  setImmediate: function(func: Function, ...args: any) {
     const id = _allocateCallback(
       () => func.apply(undefined, args),
       'setImmediate',