diff --git a/client/src/telethon/_impl/mtsender/sender.py b/client/src/telethon/_impl/mtsender/sender.py
index fd9f31a2..eb9facd3 100644
--- a/client/src/telethon/_impl/mtsender/sender.py
+++ b/client/src/telethon/_impl/mtsender/sender.py
@@ -287,7 +287,7 @@ class Sender:
             return self._mtp.auth_key
 
 
-async def connect(transport, addr):
+async def connect(transport: Transport, addr: str) -> Tuple[Sender, Enqueuer]:
     sender, enqueuer = await Sender.connect(transport, Plain(), addr)
     return await generate_auth_key(sender, enqueuer)
 
diff --git a/client/tests/mtproto_test.py b/client/tests/mtproto_test.py
index 4cdfc1c4..4c256878 100644
--- a/client/tests/mtproto_test.py
+++ b/client/tests/mtproto_test.py
@@ -1,6 +1,7 @@
 import struct
 
 from pytest import raises
+from telethon._impl.crypto.auth_key import AuthKey
 from telethon._impl.mtproto.mtp import Encrypted, Plain, RpcError
 from telethon._impl.tl.mtproto.types import RpcError as GeneratedRpcError
 
@@ -70,8 +71,8 @@ REQUEST = b"Hey!"
 REQUEST_B = b"Bye!"
 
 
-def auth_key() -> bytes:
-    return bytes(256)
+def auth_key() -> AuthKey:
+    return AuthKey.from_bytes(bytes(256))
 
 
 def ensure_buffer_is_message(buffer: bytes, body: bytes, seq_no: int) -> None:
diff --git a/client/tests/mtsender_test.py b/client/tests/mtsender_test.py
index 031c5f85..b187fb7f 100644
--- a/client/tests/mtsender_test.py
+++ b/client/tests/mtsender_test.py
@@ -1,6 +1,7 @@
 import asyncio
 import logging
 
+from pytest import LogCaptureFixture
 from telethon._impl.mtproto.transport.full import Full
 from telethon._impl.mtsender.sender import connect
 
@@ -11,13 +12,13 @@ TELEGRAM_DEFAULT_TEST_DC = TELEGRAM_TEST_DC_2
 TEST_TIMEOUT = 10000
 
 
-def test_invoke_encrypted_method(caplog) -> None:
+def test_invoke_encrypted_method(caplog: LogCaptureFixture) -> None:
     caplog.set_level(logging.DEBUG)
 
-    async def func():
+    async def func() -> None:
         deadline = asyncio.get_running_loop().time() + TEST_TIMEOUT
 
-        def timeout():
+        def timeout() -> float:
             return deadline - asyncio.get_running_loop().time()
 
         sender, enqueuer = await asyncio.wait_for(
diff --git a/client/tests/transport/abridged_test.py b/client/tests/transport/abridged_test.py
index 71af5dc1..91a85e10 100644
--- a/client/tests/transport/abridged_test.py
+++ b/client/tests/transport/abridged_test.py
@@ -11,7 +11,7 @@ class Output(bytearray):
         self += data
 
 
-def setup_pack(n: int) -> Tuple[Abridged, bytes, bytearray]:
+def setup_pack(n: int) -> Tuple[Abridged, bytes, Output]:
     input = bytes(x & 0xFF for x in range(n))
     return Abridged(), input, Output()
 
diff --git a/client/tests/transport/full_test.py b/client/tests/transport/full_test.py
index b85827fc..a961b7ef 100644
--- a/client/tests/transport/full_test.py
+++ b/client/tests/transport/full_test.py
@@ -11,7 +11,7 @@ class Output(bytearray):
         self += data
 
 
-def setup_pack(n: int) -> Tuple[Full, bytes, bytearray]:
+def setup_pack(n: int) -> Tuple[Full, bytes, Output]:
     input = bytes(x & 0xFF for x in range(n))
     return Full(), input, Output()
 
diff --git a/client/tests/transport/intermediate_test.py b/client/tests/transport/intermediate_test.py
index b3a6efe8..d35df085 100644
--- a/client/tests/transport/intermediate_test.py
+++ b/client/tests/transport/intermediate_test.py
@@ -11,7 +11,7 @@ class Output(bytearray):
         self += data
 
 
-def setup_pack(n: int) -> Tuple[Intermediate, bytes, bytearray]:
+def setup_pack(n: int) -> Tuple[Intermediate, bytes, Output]:
     input = bytes(x & 0xFF for x in range(n))
     return Intermediate(), input, Output()