diff --git a/src/renderers/shared/fiber/ReactFiberDevToolsHook.js b/src/renderers/shared/fiber/ReactFiberDevToolsHook.js
index 6f85684fb682..ef0e0b2c682c 100644
--- a/src/renderers/shared/fiber/ReactFiberDevToolsHook.js
+++ b/src/renderers/shared/fiber/ReactFiberDevToolsHook.js
@@ -12,6 +12,8 @@
 
 /* globals __REACT_DEVTOOLS_GLOBAL_HOOK__ */
 
+declare var __REACT_DEVTOOLS_GLOBAL_HOOK__ : Object | void;
+
 'use strict';
 
 import type { Fiber } from 'ReactFiber';