diff --git a/packages/client/src/methods/files/download-buffer.ts b/packages/client/src/methods/files/download-buffer.ts
index a945584a..b7d89133 100644
--- a/packages/client/src/methods/files/download-buffer.ts
+++ b/packages/client/src/methods/files/download-buffer.ts
@@ -16,7 +16,7 @@ export async function downloadAsBuffer(
 ): Promise<Buffer> {
     if (
         params.location instanceof FileLocation &&
-        params.location.location instanceof Buffer
+        Buffer.isBuffer(params.location.location)
     ) {
         return params.location.location
     }
diff --git a/packages/client/src/methods/files/download-file.ts b/packages/client/src/methods/files/download-file.ts
index b78b58be..9262240d 100644
--- a/packages/client/src/methods/files/download-file.ts
+++ b/packages/client/src/methods/files/download-file.ts
@@ -30,7 +30,7 @@ export function downloadToFile(
 
     if (
         params.location instanceof FileLocation &&
-        params.location.location instanceof Buffer
+        Buffer.isBuffer(params.location.location)
     ) {
         // early return for inline files
         const buf = params.location.location
diff --git a/packages/client/src/methods/files/download-iterable.ts b/packages/client/src/methods/files/download-iterable.ts
index 8c0840e5..e263f767 100644
--- a/packages/client/src/methods/files/download-iterable.ts
+++ b/packages/client/src/methods/files/download-iterable.ts
@@ -46,7 +46,7 @@ export async function* downloadAsIterable(
             ;(input as tl.Mutable<FileLocation>).location = input.location()
         }
 
-        if (input.location instanceof Buffer) {
+        if (Buffer.isBuffer(input.location)) {
             yield input.location
             return
         }
diff --git a/packages/client/src/methods/files/download-stream.ts b/packages/client/src/methods/files/download-stream.ts
index d5f6b98f..6a74ec88 100644
--- a/packages/client/src/methods/files/download-stream.ts
+++ b/packages/client/src/methods/files/download-stream.ts
@@ -16,7 +16,7 @@ export function downloadAsStream(
 ): Readable {
     if (
         params.location instanceof FileLocation &&
-        params.location.location instanceof Buffer
+        Buffer.isBuffer(params.location.location)
     ) {
         return bufferToStream(params.location.location)
     }
diff --git a/packages/client/src/methods/files/upload-file.ts b/packages/client/src/methods/files/upload-file.ts
index 6d4d7adc..cfe96eac 100644
--- a/packages/client/src/methods/files/upload-file.ts
+++ b/packages/client/src/methods/files/upload-file.ts
@@ -95,7 +95,7 @@ export async function uploadFile(
     let fileName = 'unnamed'
     let fileMime = params.fileMime
 
-    if (file instanceof Buffer) {
+    if (Buffer.isBuffer(file)) {
         fileSize = file.length
         file = bufferToStream(file)
     }
@@ -180,8 +180,8 @@ export async function uploadFile(
             throw new MtCuteArgumentError(
                 `Unexpected EOS (there were only ${idx} parts, but expected ${partCount})`
             )
-        // even though typescript seems to guarantee this, we can't be sure because its js after all
-        if (!(part instanceof Buffer))
+
+        if (!Buffer.isBuffer(part))
             throw new MtCuteArgumentError(`Part ${idx} was not a Buffer!`)
         if (part.length > partSize)
             throw new MtCuteArgumentError(
diff --git a/packages/core/src/network/mtproto-session.ts b/packages/core/src/network/mtproto-session.ts
index 3fe89e6e..9c358dca 100644
--- a/packages/core/src/network/mtproto-session.ts
+++ b/packages/core/src/network/mtproto-session.ts
@@ -70,9 +70,9 @@ export class MtprotoSession {
         if (!this._authKey) throw new Error('Keys are not set up!')
 
         const length =
-            message.constructor === Buffer
+            Buffer.isBuffer(message)
                 ? message.length
-                : SerializationCounter.countNeededBytes(message as tl.TlObject)
+                : SerializationCounter.countNeededBytes(message)
         let padding =
             (32 /* header size */ + length + 12) /* min padding */ % 16
         padding = 12 + (padding ? 16 - padding : 0)
@@ -83,7 +83,7 @@ export class MtprotoSession {
         encryptedWriter.long(messageId)
         encryptedWriter.int32(seqNo)
         encryptedWriter.uint32(length)
-        if (message.constructor === Buffer) encryptedWriter.raw(message)
+        if (Buffer.isBuffer(message)) encryptedWriter.raw(message)
         else encryptedWriter.object(message as tl.TlObject)
         encryptedWriter.raw(randomBytes(padding))
 
diff --git a/packages/core/src/network/transports/ws-obfuscated.ts b/packages/core/src/network/transports/ws-obfuscated.ts
index b8996471..b2afdc89 100644
--- a/packages/core/src/network/transports/ws-obfuscated.ts
+++ b/packages/core/src/network/transports/ws-obfuscated.ts
@@ -77,8 +77,8 @@ export class ObfuscatedPacketCodec extends EventEmitter implements PacketCodec {
 
     feed(data: Buffer): void {
         const dec = this._decryptor!.decrypt(data)
-        if (dec.constructor === Buffer) this._inner.feed(dec)
-        else (dec as Promise<Buffer>).then((dec) => this._inner.feed(dec))
+        if (Buffer.isBuffer(dec)) this._inner.feed(dec)
+        else dec.then((dec) => this._inner.feed(dec))
     }
 
     reset(): void {