diff --git a/data/telegram.org/js/telegram-webview.js b/data/telegram.org/js/telegram-webview.js
index 8e05f277bf..7fdea422b0 100644
--- a/data/telegram.org/js/telegram-webview.js
+++ b/data/telegram.org/js/telegram-webview.js
@@ -450,9 +450,11 @@
     mainButton.setParams = setParams;
     mainButton.setText = function(text) {
       mainButton.text = text;
+      return mainButton;
     };
     mainButton.onClick = function(callback) {
       onClickCallback = callback;
+      return mainButton;
     };
     mainButton.show = function() {
       return mainButton.setParams({is_visible: true});
diff --git a/data/webappcontent.telegram.org/demo.html b/data/webappcontent.telegram.org/demo.html
index 070fc8a625..e284a724c5 100644
--- a/data/webappcontent.telegram.org/demo.html
+++ b/data/webappcontent.telegram.org/demo.html
@@ -150,7 +150,7 @@ function sendMessage(msg_id, with_webview) {
   $('#btn_status').text('Sending...').removeClass('ok err').show();
   $.ajax('/demo/sendMessage', {
     type: 'POST',
-    data: {query_id: WebAppData.query_id, msg_id: msg_id || '', with_webview: !WebAppData.receiver && with_webview ? 1 : 0},
+    data: {_auth: WebAppDataRaw, query_id: WebAppData.query_id, msg_id: msg_id || '', with_webview: !WebAppData.receiver && with_webview ? 1 : 0},
     dataType: 'json',
     success: function(result) {
       $('button').prop('disabled', false);
@@ -173,6 +173,35 @@ function sendMessage(msg_id, with_webview) {
     }
   });
 }
+function changeButton() {
+  $('button').prop('disabled', true);
+  $('#btn_status').text('Changing button...').removeClass('ok err').show();
+  $.ajax('/demo/changeMenuButton', {
+    type: 'POST',
+    data: {_auth: WebAppDataRaw},
+    dataType: 'json',
+    success: function(result) {
+      $('button').prop('disabled', false);
+      if (result.response) {
+        if (result.response.ok) {
+          $('#btn_status').html('Button changed!').addClass('ok').show();
+          Telegram.WebApp.close();
+        } else {
+          $('#btn_status').text(result.response.description).addClass('err').show();
+          alert(result.response.description);
+        }
+      } else {
+        $('#btn_status').text('Unknown error').addClass('err').show();
+        alert('Unknown error');
+      }
+    },
+    error: function(xhr) {
+      $('button').prop('disabled', false);
+      $('#btn_status').text('Server error').addClass('err').show();
+      alert('Server error');
+    }
+  });
+}
 function byteLength(str) {
   if (window.Blob) {
     try { return new Blob([str]).size; } catch (e) {}
@@ -254,7 +283,7 @@ if (WebAppData.query_id && WebAppDataRaw) {
   $('#webview_data_status').show();
   $.ajax('/demo/checkData', {
     type: 'POST',
-    data: {data: WebAppDataRaw},
+    data: {_auth: WebAppDataRaw},
     dataType: 'json',
     success: function(result) {
       if (result.ok) {