diff --git a/Libraries/Modal/Modal.js b/Libraries/Modal/Modal.js
index cc5206841..782ec78a3 100644
--- a/Libraries/Modal/Modal.js
+++ b/Libraries/Modal/Modal.js
@@ -128,6 +128,10 @@ class Modal extends React.Component {
     visible: true,
   };
 
+  static contextTypes = {
+    rootTag: React.PropTypes.number,
+  };
+
   render(): ?React.Element<any> {
     if (this.props.visible === false) {
       return null;
@@ -147,7 +151,7 @@ class Modal extends React.Component {
     }
 
     const innerChildren = __DEV__ ?
-      ( <AppContainer>
+      ( <AppContainer rootTag={this.context.rootTag}>
           {this.props.children}
         </AppContainer>) :
       this.props.children;
diff --git a/Libraries/ReactNative/AppContainer.js b/Libraries/ReactNative/AppContainer.js
index 8b3a76b8c..d7680bd85 100644
--- a/Libraries/ReactNative/AppContainer.js
+++ b/Libraries/ReactNative/AppContainer.js
@@ -19,13 +19,12 @@ const ReactNative = require('ReactNative');
 const StyleSheet = require('StyleSheet');
 const View = require('View');
 
-// TODO (fkg): make rootTag required
 type Context = {
-  rootTag: ?number,
+  rootTag: number,
 };
 type Props = {
   children?: React.Children,
-  rootTag?: number,
+  rootTag: number,
 };
 type State = {
   inspector: ?React.Element<*>,