diff --git a/src/webview/js/generatedEs3.js b/src/webview/js/generatedEs3.js
index bcd5acfe35a..3404fec6839 100644
--- a/src/webview/js/generatedEs3.js
+++ b/src/webview/js/generatedEs3.js
@@ -36,6 +36,55 @@ var compiledWebviewJs = (function (exports) {
     return Constructor;
   }
 
+  function _defineProperty(obj, key, value) {
+    if (key in obj) {
+      Object.defineProperty(obj, key, {
+        value: value,
+        enumerable: true,
+        configurable: true,
+        writable: true
+      });
+    } else {
+      obj[key] = value;
+    }
+
+    return obj;
+  }
+
+  function ownKeys(object, enumerableOnly) {
+    var keys = Object.keys(object);
+
+    if (Object.getOwnPropertySymbols) {
+      var symbols = Object.getOwnPropertySymbols(object);
+      if (enumerableOnly) symbols = symbols.filter(function (sym) {
+        return Object.getOwnPropertyDescriptor(object, sym).enumerable;
+      });
+      keys.push.apply(keys, symbols);
+    }
+
+    return keys;
+  }
+
+  function _objectSpread2(target) {
+    for (var i = 1; i < arguments.length; i++) {
+      var source = arguments[i] != null ? arguments[i] : {};
+
+      if (i % 2) {
+        ownKeys(Object(source), true).forEach(function (key) {
+          _defineProperty(target, key, source[key]);
+        });
+      } else if (Object.getOwnPropertyDescriptors) {
+        Object.defineProperties(target, Object.getOwnPropertyDescriptors(source));
+      } else {
+        ownKeys(Object(source)).forEach(function (key) {
+          Object.defineProperty(target, key, Object.getOwnPropertyDescriptor(source, key));
+        });
+      }
+    }
+
+    return target;
+  }
+
   var sendMessage = (function (msg) {
     window.ReactNativeWebView.postMessage(JSON.stringify(msg));
   });
@@ -610,7 +659,11 @@ var compiledWebviewJs = (function (exports) {
     sendScrollMessageIfListShort();
   };
 
-  var handleInitialLoad = function handleInitialLoad(platformOS, scrollMessageId, auth) {
+  var handleInitialLoad = function handleInitialLoad(platformOS, scrollMessageId, rawAuth) {
+    var auth = _objectSpread2(_objectSpread2({}, rawAuth), {}, {
+      realm: rawAuth.realm
+    });
+
     if (platformOS === 'ios') {
       window.addEventListener('message', handleMessageEvent);
     } else {
diff --git a/src/webview/js/js.js b/src/webview/js/js.js
index 30621d659f9..f31adfaeea2 100644
--- a/src/webview/js/js.js
+++ b/src/webview/js/js.js
@@ -544,8 +544,11 @@ const handleUpdateEventContent = (uevent: WebViewUpdateEventContent) => {
 export const handleInitialLoad = (
   platformOS: string,
   scrollMessageId: number | null,
-  auth: Auth,
+  // In an upcoming commit, the `realm` part of an `Auth` object will
+  // be a URL object. It'll be passed here in its stringified form.
+  rawAuth: {| ...$Diff<Auth, { realm: mixed }>, realm: string |},
 ) => {
+  const auth: Auth = { ...rawAuth, realm: rawAuth.realm };
   // Since its version 5.x, the `react-native-webview` library dispatches our
   // `message` events at `window` on iOS but `document` on Android.
   if (platformOS === 'ios') {