diff --git a/.gitignore b/.gitignore
index 1e8f5ba9..11e75cda 100644
--- a/.gitignore
+++ b/.gitignore
@@ -184,4 +184,4 @@ tests/interop/js_libp2p/js_node/src/node_modules/
 tests/interop/js_libp2p/js_node/src/package-lock.json
 
 # Sphinx documentation build
-_build/
\ No newline at end of file
+_build/
diff --git a/libp2p/__init__.py b/libp2p/__init__.py
index 9c99c211..b03f494f 100644
--- a/libp2p/__init__.py
+++ b/libp2p/__init__.py
@@ -203,7 +203,7 @@ def new_swarm(
 
     id_opt = generate_peer_id_from(key_pair)
 
-    transport: TCP | QUICTransport
+    transport: TCP | QUICTransport | ITransport
     quic_transport_opt = connection_config if isinstance(connection_config, QUICTransportConfig) else None
 
     if listen_addrs is None:
@@ -261,7 +261,6 @@ def new_swarm(
     )
 
     # Create transport based on listen_addrs or default to TCP
-    transport: ITransport
     if listen_addrs is None:
         transport = TCP()
     else:
@@ -274,7 +273,7 @@ def new_swarm(
             if addr.__contains__("tcp"):
                 transport = TCP()
             elif addr.__contains__("quic"):
-                raise ValueError("QUIC not yet supported")
+                transport = QUICTransport(key_pair.private_key, config=quic_transport_opt)
             else:
                 supported_protocols = get_supported_transport_protocols()
                 raise ValueError(
diff --git a/libp2p/network/swarm.py b/libp2p/network/swarm.py
index f78b4fa8..94d9c7a3 100644
--- a/libp2p/network/swarm.py
+++ b/libp2p/network/swarm.py
@@ -491,9 +491,8 @@ class Swarm(Service, INetworkService):
             logger.debug(f"Swarm.listen processing multiaddr: {maddr}")
             if str(maddr) in self.listeners:
                 logger.debug(f"Swarm.listen: listener already exists for {maddr}")
-                return True
-            success_count += 1
-            continue
+                success_count += 1
+                continue
 
             async def conn_handler(
                 read_write_closer: ReadWriteCloser, maddr: Multiaddr = maddr
@@ -557,6 +556,7 @@ class Swarm(Service, INetworkService):
                 #   I/O agnostic, we should change the API.
                 if self.listener_nursery is None:
                     raise SwarmException("swarm instance hasn't been run")
+                assert self.listener_nursery is not None  # For type checker
                 logger.debug(f"Swarm.listen: calling listener.listen for {maddr}")
                 await listener.listen(maddr, self.listener_nursery)
                 logger.debug(f"Swarm.listen: listener.listen completed for {maddr}")
diff --git a/libp2p/transport/quic/connection.py b/libp2p/transport/quic/connection.py
index 428acd83..fb4cff4a 100644
--- a/libp2p/transport/quic/connection.py
+++ b/libp2p/transport/quic/connection.py
@@ -8,7 +8,7 @@ from collections.abc import Awaitable, Callable
 import logging
 import socket
 import time
-from typing import TYPE_CHECKING, Any, Optional, cast
+from typing import TYPE_CHECKING, Any, Optional
 
 from aioquic.quic import events
 from aioquic.quic.connection import QuicConnection
@@ -871,9 +871,11 @@ class QUICConnection(IRawConnection, IMuxedConn):
         # Process events by type
         for event_type, event_list in events_by_type.items():
             if event_type == type(events.StreamDataReceived).__name__:
-                await self._handle_stream_data_batch(
-                    cast(list[events.StreamDataReceived], event_list)
-                )
+                # Filter to only StreamDataReceived events
+                stream_data_events = [
+                    e for e in event_list if isinstance(e, events.StreamDataReceived)
+                ]
+                await self._handle_stream_data_batch(stream_data_events)
             else:
                 # Process other events individually
                 for event in event_list: