diff --git a/src/isomorphic/classic/element/ReactCurrentOwner.js b/src/isomorphic/classic/element/ReactCurrentOwner.js
index e47505f413..da5786e875 100644
--- a/src/isomorphic/classic/element/ReactCurrentOwner.js
+++ b/src/isomorphic/classic/element/ReactCurrentOwner.js
@@ -7,10 +7,13 @@
  * of patent rights can be found in the PATENTS file in the same directory.
  *
  * @providesModule ReactCurrentOwner
+ * @flow
  */
 
 'use strict';
 
+import type { ReactInstance } from 'ReactInstanceType';
+
 /**
  * Keeps track of the current owner.
  *
@@ -23,7 +26,7 @@ var ReactCurrentOwner = {
    * @internal
    * @type {ReactComponent}
    */
-  current: null,
+  current: (null: null | ReactInstance),
 
 };
 
diff --git a/src/renderers/shared/stack/reconciler/ReactInstanceType.js b/src/renderers/shared/stack/reconciler/ReactInstanceType.js
index b27d3371c7..d647f4afc9 100644
--- a/src/renderers/shared/stack/reconciler/ReactInstanceType.js
+++ b/src/renderers/shared/stack/reconciler/ReactInstanceType.js
@@ -34,4 +34,5 @@ export type ReactInstance = {
   _mountImage: any,
   // __DEV__
   _debugID: DebugID,
+  _warnedAboutRefsInRender: bool,
 };