diff --git a/src/api/gramjs/methods/bots.ts b/src/api/gramjs/methods/bots.ts
index 77350238c..f47c0e1b8 100644
--- a/src/api/gramjs/methods/bots.ts
+++ b/src/api/gramjs/methods/bots.ts
@@ -10,22 +10,23 @@ import { buildApiUser } from '../apiBuilders/users';
 import { buildApiBotInlineMediaResult, buildApiBotInlineResult, buildBotSwitchPm } from '../apiBuilders/bots';
 import { buildApiChatFromPreview } from '../apiBuilders/chats';
 import { addEntitiesWithPhotosToLocalDb, addUserToLocalDb, deserializeBytes } from '../helpers';
+import { omitVirtualClassFields } from '../apiBuilders/helpers';
 
 export function init() {
 }
 
-export function answerCallbackButton(
-  {
-    chatId, accessHash, messageId, data,
-  }: {
-    chatId: string; accessHash?: string; messageId: number; data: string;
-  },
-) {
-  return invokeRequest(new GramJs.messages.GetBotCallbackAnswer({
+export async function answerCallbackButton({
+  chatId, accessHash, messageId, data,
+}: {
+  chatId: string; accessHash?: string; messageId: number; data: string;
+}) {
+  const result = await invokeRequest(new GramJs.messages.GetBotCallbackAnswer({
     peer: buildInputPeer(chatId, accessHash),
     msgId: messageId,
     data: deserializeBytes(data),
   }));
+
+  return result ? omitVirtualClassFields(result) : undefined;
 }
 
 export async function fetchTopInlineBots() {
diff --git a/src/api/gramjs/methods/calls.ts b/src/api/gramjs/methods/calls.ts
index 8476021b4..ce22d7c0f 100644
--- a/src/api/gramjs/methods/calls.ts
+++ b/src/api/gramjs/methods/calls.ts
@@ -164,7 +164,7 @@ export async function joinGroupCall({
       data: JSON.stringify(params),
     }),
     inviteHash,
-  }), true);
+  }));
 
   if (!result) return undefined;
 
@@ -187,7 +187,7 @@ export async function createGroupCall({
   const result = await invokeRequest(new GramJs.phone.CreateGroupCall({
     peer: buildInputPeer(peer.id, peer.accessHash),
     randomId,
-  }), true);
+  }));
 
   if (!result) return undefined;
 
diff --git a/src/api/gramjs/methods/chats.ts b/src/api/gramjs/methods/chats.ts
index c7bc0db48..3fb4abd69 100644
--- a/src/api/gramjs/methods/chats.ts
+++ b/src/api/gramjs/methods/chats.ts
@@ -508,7 +508,7 @@ export async function createChannel({
     broadcast: true,
     title,
     about,
-  }), true);
+  }));
 
   // `createChannel` can return a lot of different update types according to docs,
   // but currently channel creation returns only `Updates` type.
@@ -537,7 +537,7 @@ export async function createChannel({
       await invokeRequest(new GramJs.channels.InviteToChannel({
         channel: buildInputEntity(channel.id, channel.accessHash) as GramJs.InputChannel,
         users: users.map(({ id, accessHash }) => buildInputEntity(id, accessHash)) as GramJs.InputUser[],
-      }), true, noErrorUpdate);
+      }), undefined, noErrorUpdate);
     } catch (err) {
       // `noErrorUpdate` will cause an exception which we don't want either
     }
@@ -606,7 +606,7 @@ export async function createGroupChat({
   const result = await invokeRequest(new GramJs.messages.CreateChat({
     title,
     users: users.map(({ id, accessHash }) => buildInputEntity(id, accessHash)) as GramJs.InputUser[],
-  }), true, true);
+  }), undefined, true);
 
   // `createChat` can return a lot of different update types according to docs,
   // but currently chat creation returns only `Updates` type.
@@ -975,12 +975,12 @@ export function setDiscussionGroup({
   return invokeRequest(new GramJs.channels.SetDiscussionGroup({
     broadcast: buildInputPeer(channel.id, channel.accessHash),
     group: chat ? buildInputPeer(chat.id, chat.accessHash) : new GramJs.InputChannelEmpty(),
-  }));
+  }), true);
 }
 
 export async function migrateChat(chat: ApiChat) {
   const result = await invokeRequest(
-    new GramJs.messages.MigrateChat({ chatId: buildInputEntity(chat.id) as BigInt.BigInteger }), true,
+    new GramJs.messages.MigrateChat({ chatId: buildInputEntity(chat.id) as BigInt.BigInteger }),
   );
 
   // `migrateChat` can return a lot of different update types according to docs,
@@ -1049,16 +1049,16 @@ export async function openChatByInvite(hash: string) {
   return { chatId: chat.id };
 }
 
-export function addChatMembers(chat: ApiChat, users: ApiUser[], noErrorUpdate = false) {
+export async function addChatMembers(chat: ApiChat, users: ApiUser[], noErrorUpdate = false) {
   try {
     if (chat.type === 'chatTypeChannel' || chat.type === 'chatTypeSuperGroup') {
-      return invokeRequest(new GramJs.channels.InviteToChannel({
+      return await invokeRequest(new GramJs.channels.InviteToChannel({
         channel: buildInputEntity(chat.id, chat.accessHash) as GramJs.InputChannel,
         users: users.map((user) => buildInputEntity(user.id, user.accessHash)) as GramJs.InputUser[],
       }), true, noErrorUpdate);
     }
 
-    return Promise.all(users.map((user) => {
+    return await Promise.all(users.map((user) => {
       return invokeRequest(new GramJs.messages.AddChatUser({
         chatId: buildInputEntity(chat.id) as BigInt.BigInteger,
         userId: buildInputEntity(user.id, user.accessHash) as GramJs.InputUser,
@@ -1139,7 +1139,7 @@ function updateLocalDb(result: (
 }
 
 export async function importChatInvite({ hash }: { hash: string }) {
-  const updates = await invokeRequest(new GramJs.messages.ImportChatInvite({ hash }), true);
+  const updates = await invokeRequest(new GramJs.messages.ImportChatInvite({ hash }));
   if (!(updates instanceof GramJs.Updates) || !updates.chats.length) {
     return undefined;
   }
diff --git a/src/api/gramjs/methods/client.ts b/src/api/gramjs/methods/client.ts
index d7ea953dc..21705fa7f 100644
--- a/src/api/gramjs/methods/client.ts
+++ b/src/api/gramjs/methods/client.ts
@@ -161,9 +161,21 @@ function handleGramJsUpdate(update: any) {
 
 export async function invokeRequest<T extends GramJs.AnyRequest>(
   request: T,
-  shouldHandleUpdates = false,
+  shouldReturnTrue: true,
+  shouldThrow?: boolean,
+): Promise<true | undefined>;
+
+export async function invokeRequest<T extends GramJs.AnyRequest>(
+  request: T,
+  shouldReturnTrue?: boolean,
+  shouldThrow?: boolean,
+): Promise<T['__response'] | undefined>;
+
+export async function invokeRequest<T extends GramJs.AnyRequest>(
+  request: T,
+  shouldReturnTrue = false,
   shouldThrow = false,
-): Promise<T['__response'] | undefined> {
+) {
   if (!isConnected) {
     if (DEBUG) {
       // eslint-disable-next-line no-console
@@ -186,35 +198,9 @@ export async function invokeRequest<T extends GramJs.AnyRequest>(
       console.log(`[GramJs/client] INVOKE RESPONSE ${request.className}`, result);
     }
 
-    if (shouldHandleUpdates) {
-      type ResultWithUpdates =
-        typeof result
-        & { updates?: GramJs.Updates | GramJs.UpdatesCombined };
+    handleUpdatesFromRequest(request, result);
 
-      let updatesContainer;
-      if (result instanceof GramJs.Updates || result instanceof GramJs.UpdatesCombined) {
-        updatesContainer = result;
-      } else if ('updates' in (result as ResultWithUpdates) && (
-        (result as ResultWithUpdates).updates instanceof GramJs.Updates
-        || (result as ResultWithUpdates).updates instanceof GramJs.UpdatesCombined
-      )) {
-        updatesContainer = (result as ResultWithUpdates).updates;
-      }
-
-      if (updatesContainer) {
-        injectUpdateEntities(updatesContainer);
-
-        updatesContainer.updates.forEach((update) => {
-          updater(update, request);
-        });
-      } else if (result instanceof GramJs.UpdatesTooLong) {
-        // TODO Implement
-      } else {
-        updater(result as GramJs.TypeUpdates, request);
-      }
-    }
-
-    return result;
+    return shouldReturnTrue ? result && true : result;
   } catch (err) {
     if (DEBUG) {
       // eslint-disable-next-line no-console
@@ -233,6 +219,36 @@ export async function invokeRequest<T extends GramJs.AnyRequest>(
   }
 }
 
+function handleUpdatesFromRequest<T extends GramJs.AnyRequest>(request: T, result: T['__response']) {
+  let manyUpdates;
+  let singleUpdate;
+
+  if (result instanceof GramJs.UpdatesCombined || result instanceof GramJs.Updates) {
+    manyUpdates = result;
+  } else if (typeof result === 'object' && 'updates' in result && (
+    result.updates instanceof GramJs.Updates || result.updates instanceof GramJs.UpdatesCombined
+  )) {
+    manyUpdates = result.updates;
+  } else if (
+    result instanceof GramJs.UpdateShortMessage
+    || result instanceof GramJs.UpdateShortChatMessage
+    || result instanceof GramJs.UpdateShort
+    || result instanceof GramJs.UpdateShortSentMessage
+  ) {
+    singleUpdate = result;
+  }
+
+  if (manyUpdates) {
+    injectUpdateEntities(manyUpdates);
+
+    manyUpdates.updates.forEach((update) => {
+      updater(update, request);
+    });
+  } else if (singleUpdate) {
+    updater(singleUpdate, request);
+  }
+}
+
 export function downloadMedia(
   args: { url: string; mediaFormat: ApiMediaFormat; start?: number; end?: number; isHtmlAllowed?: boolean },
   onProgress?: ApiOnProgress,
diff --git a/src/api/gramjs/methods/management.ts b/src/api/gramjs/methods/management.ts
index 73c98a485..bb555809a 100644
--- a/src/api/gramjs/methods/management.ts
+++ b/src/api/gramjs/methods/management.ts
@@ -10,19 +10,11 @@ export function init(_onUpdate: OnApiUpdate) {
   onUpdate = _onUpdate;
 }
 
-export async function checkChatUsername(
-  { username }: { username: string },
-) {
-  try {
-    const result = await invokeRequest(new GramJs.channels.CheckUsername({
-      channel: new GramJs.InputChannelEmpty(),
-      username,
-    }), undefined, true);
-
-    return result!;
-  } catch (err) {
-    return false;
-  }
+export function checkChatUsername({ username }: { username: string }) {
+  return invokeRequest(new GramJs.channels.CheckUsername({
+    channel: new GramJs.InputChannelEmpty(),
+    username,
+  }));
 }
 
 export async function setChatUsername(
diff --git a/src/api/gramjs/methods/settings.ts b/src/api/gramjs/methods/settings.ts
index d25b1497b..4839de37c 100644
--- a/src/api/gramjs/methods/settings.ts
+++ b/src/api/gramjs/methods/settings.ts
@@ -48,7 +48,7 @@ export function updateProfile({
     firstName: firstName || '',
     lastName: lastName || '',
     about: about || '',
-  }));
+  }), true);
 }
 
 export function checkUsername(username: string) {
@@ -56,14 +56,14 @@ export function checkUsername(username: string) {
 }
 
 export function updateUsername(username: string) {
-  return invokeRequest(new GramJs.account.UpdateUsername({ username }));
+  return invokeRequest(new GramJs.account.UpdateUsername({ username }), true);
 }
 
 export async function updateProfilePhoto(file: File) {
   const inputFile = await uploadFile(file);
   return invokeRequest(new GramJs.photos.UploadProfilePhoto({
     file: inputFile,
-  }));
+  }), true);
 }
 
 export async function uploadProfilePhoto(file: File) {
@@ -311,7 +311,7 @@ export async function fetchLangPack({ sourceLangPacks, langCode }: {
     return undefined;
   }
 
-  return { langPack: Object.assign({}, ...collections.reverse()) };
+  return { langPack: Object.assign({}, ...collections.reverse()) as typeof collections[0] };
 }
 
 export async function fetchLangStrings({ langPack, langCode, keys }: {
diff --git a/src/api/gramjs/methods/users.ts b/src/api/gramjs/methods/users.ts
index 89073c0fa..aef49542a 100644
--- a/src/api/gramjs/methods/users.ts
+++ b/src/api/gramjs/methods/users.ts
@@ -157,7 +157,7 @@ export function updateContact({
       firstName: firstName || '',
       lastName: lastName || '',
     })],
-  }));
+  }), true);
 }
 
 export function addContact({
diff --git a/src/api/gramjs/worker/provider.ts b/src/api/gramjs/worker/provider.ts
index d1a4de9e1..ff53748b5 100644
--- a/src/api/gramjs/worker/provider.ts
+++ b/src/api/gramjs/worker/provider.ts
@@ -1,6 +1,7 @@
+import { Api } from '../../../lib/gramjs';
 import { ApiInitialArgs, ApiOnProgress, OnApiUpdate } from '../../types';
 import { Methods, MethodArgs, MethodResponse } from '../methods/types';
-import { WorkerMessageEvent, ThenArg, OriginRequest } from './types';
+import { WorkerMessageEvent, OriginRequest } from './types';
 
 import { DEBUG } from '../../../config';
 import generateIdFor from '../../../util/generateIdFor';
@@ -53,11 +54,36 @@ export function callApi<T extends keyof Methods>(fnName: T, ...args: MethodArgs<
     return undefined;
   }
 
-  return makeRequest({
+  const promise = makeRequest({
     type: 'callMethod',
     name: fnName,
     args,
-  }) as MethodResponse<T>;
+  });
+
+  // Some TypeScript magic to make sure `VirtualClass` is never returned from any method
+  if (DEBUG) {
+    (async () => {
+      try {
+        type ForbiddenTypes =
+          Api.VirtualClass<any>
+          | (Api.VirtualClass<any> | undefined)[];
+        type ForbiddenResponses =
+          ForbiddenTypes
+          | (AnyLiteral & { [k: string]: ForbiddenTypes });
+
+        // Unwrap all chained promises
+        const response = await promise;
+        // Make sure responses do not include `VirtualClass` instances
+        const allowedResponse: Exclude<typeof response, ForbiddenResponses> = response;
+        // Suppress "unused variable" constraint
+        void allowedResponse;
+      } catch (err) {
+        // Do noting
+      }
+    })();
+  }
+
+  return promise as MethodResponse<T>;
 }
 
 export function cancelApiProgress(progressCallback: ApiOnProgress) {
@@ -105,7 +131,7 @@ function makeRequest(message: OriginRequest) {
   const requestState = { messageId } as RequestStates;
 
   // Re-wrap type because of `postMessage`
-  const promise: Promise<ThenArg<MethodResponse<keyof Methods>>> = new Promise((resolve, reject) => {
+  const promise: Promise<MethodResponse<keyof Methods>> = new Promise((resolve, reject) => {
     Object.assign(requestState, { resolve, reject });
   });
 
diff --git a/src/api/gramjs/worker/worker.ts b/src/api/gramjs/worker/worker.ts
index 3c7720a14..cbfadd957 100644
--- a/src/api/gramjs/worker/worker.ts
+++ b/src/api/gramjs/worker/worker.ts
@@ -8,8 +8,6 @@ declare const self: WorkerGlobalScope;
 
 handleErrors();
 
-// TODO Re-use `util/createWorkerInterface.ts`
-
 const callbackState = new Map<string, ApiOnProgress>();
 
 if (DEBUG) {
@@ -45,6 +43,12 @@ onmessage = async (message: OriginMessageEvent) => {
         }
 
         const response = await callApi(name, ...args);
+
+        if (DEBUG && typeof response === 'object' && 'CONSTRUCTOR_ID' in response) {
+          // eslint-disable-next-line no-console
+          console.error(`[GramJs/worker] \`${name}\`: Unexpected response \`${(response as any).className}\``);
+        }
+
         const { arrayBuffer } = (typeof response === 'object' && 'arrayBuffer' in response && response) || {};
 
         if (messageId) {
diff --git a/src/lib/gramjs/tl/api.d.ts b/src/lib/gramjs/tl/api.d.ts
index 2a567798b..da0d2ad7b 100644
--- a/src/lib/gramjs/tl/api.d.ts
+++ b/src/lib/gramjs/tl/api.d.ts
@@ -16,8 +16,7 @@ namespace Api {
   type Client = any; // To be defined.
   type Utils = any; // To be defined.
 
-  type X = unknown;
-  type Type = unknown;
+  type X = AnyLiteral;
   type Bool = boolean;
   type int = number;
   type int128 = BigInteger;
diff --git a/src/lib/gramjs/tl/types-generator/template.js b/src/lib/gramjs/tl/types-generator/template.js
index 01bce3e6e..a5633c56d 100644
--- a/src/lib/gramjs/tl/types-generator/template.js
+++ b/src/lib/gramjs/tl/types-generator/template.js
@@ -1,5 +1,5 @@
 // Not sure what they are for.
-const WEIRD_TYPES = new Set(['Bool', 'X', 'Type'])
+const RAW_TYPES = new Set(['Bool', 'X'])
 
 module.exports = ({ types, constructors, functions }) => {
     function groupByKey(collection, key) {
@@ -55,9 +55,10 @@ ${indent}};`.trim()
     function renderRequests(requests, indent) {
         return requests.map(({ name, argsConfig, result }) => {
             const argKeys = Object.keys(argsConfig)
+            const renderedResult = renderResult(result);
 
             if (!argKeys.length) {
-                return `export class ${upperFirst(name)} extends Request<void, ${renderResult(result)}> {};`
+                return `export class ${upperFirst(name)} extends Request<void, ${renderedResult}> {};`
             }
 
             let hasRequiredArgs = argKeys.some((argName) => argName !== 'flags' && !argsConfig[argName].isFlag)
@@ -68,7 +69,7 @@ ${indent}  ${argKeys.map((argName) => `
         ${renderArg(argName, argsConfig[argName])};
       `.trim())
             .join(`\n${indent}  `)}
-${indent}}${!hasRequiredArgs ? ` | void` : ''}>, ${renderResult(result)}> {
+${indent}}${!hasRequiredArgs ? ` | void` : ''}>, ${renderedResult}> {
 ${indent}  ${argKeys.map((argName) => `
         ${renderArg(argName, argsConfig[argName])};
       `.trim())
@@ -98,7 +99,7 @@ ${indent}};`.trim()
     }
 
     function renderValueType(type, isVector, isTlType) {
-        if (WEIRD_TYPES.has(type)) {
+        if (RAW_TYPES.has(type)) {
             return type
         }
 
@@ -148,8 +149,7 @@ namespace Api {
   type Client = any; // To be defined.
   type Utils = any; // To be defined.
 
-  type X = unknown;
-  type Type = unknown;
+  type X = AnyLiteral;
   type Bool = boolean;
   type int = number;
   type int128 = BigInteger;