diff --git a/packages/react-reconciler/src/forks/ReactFiberErrorDialog.www.js b/packages/react-reconciler/src/forks/ReactFiberErrorDialog.www.js
index 80546ec198..b7cd2d59d0 100644
--- a/packages/react-reconciler/src/forks/ReactFiberErrorDialog.www.js
+++ b/packages/react-reconciler/src/forks/ReactFiberErrorDialog.www.js
@@ -9,8 +9,14 @@
 
 import type {CapturedError} from '../ReactFiberScheduler';
 
+import invariant from 'fbjs/lib/invariant';
+
 // Provided by www
 const ReactFiberErrorDialogWWW = require('ReactFiberErrorDialog');
+invariant(
+  typeof ReactFiberErrorDialogWWW.showErrorDialog === 'function',
+  'Expected ReactFiberErrorDialog.showErrorDialog to existbe a function.',
+);
 
 export function showErrorDialog(capturedError: CapturedError): boolean {
   return ReactFiberErrorDialogWWW.showErrorDialog(capturedError);