diff --git a/google/cloud/pubsublite/cloudpubsub/internal/multiplexed_publisher_client.py b/google/cloud/pubsublite/cloudpubsub/internal/multiplexed_publisher_client.py
index 249463c6..4bfe9cf5 100644
--- a/google/cloud/pubsublite/cloudpubsub/internal/multiplexed_publisher_client.py
+++ b/google/cloud/pubsublite/cloudpubsub/internal/multiplexed_publisher_client.py
@@ -47,7 +47,7 @@ def publish(
         data: bytes,
         ordering_key: str = "",
         **attrs: Mapping[str, str]
-    ) -> Future:
+    ) -> "Future[str]":
         if isinstance(topic, str):
             topic = TopicPath.parse(topic)
         publisher = self._multiplexer.get_or_create(
diff --git a/google/cloud/pubsublite/cloudpubsub/internal/multiplexed_subscriber_client.py b/google/cloud/pubsublite/cloudpubsub/internal/multiplexed_subscriber_client.py
index 3c4d9dfe..928984ae 100644
--- a/google/cloud/pubsublite/cloudpubsub/internal/multiplexed_subscriber_client.py
+++ b/google/cloud/pubsublite/cloudpubsub/internal/multiplexed_subscriber_client.py
@@ -13,7 +13,7 @@
 # limitations under the License.
 
 from concurrent.futures.thread import ThreadPoolExecutor
-from typing import Union, Optional, Set, Callable, cast
+from typing import Union, Optional, Set
 
 from google.cloud.pubsub_v1.subscriber.futures import StreamingPullFuture
 
@@ -61,13 +61,12 @@ def cancel_streaming_pull_future(fut: StreamingPullFuture):
     def subscribe(
         self,
         subscription: Union[SubscriptionPath, str],
-        callback: Callable,  # TODO(dpcollins): Change to MessageCallback,
+        callback: MessageCallback,
         per_partition_flow_control_settings: FlowControlSettings,
         fixed_partitions: Optional[Set[Partition]] = None,
     ) -> StreamingPullFuture:
         if isinstance(subscription, str):
             subscription = SubscriptionPath.parse(subscription)
-        callback = cast(MessageCallback, callback)
 
         def create_and_open():
             underlying = self._underlying_factory(
diff --git a/google/cloud/pubsublite/cloudpubsub/internal/publisher_impl.py b/google/cloud/pubsublite/cloudpubsub/internal/publisher_impl.py
index 2e66a380..7f25e77d 100644
--- a/google/cloud/pubsublite/cloudpubsub/internal/publisher_impl.py
+++ b/google/cloud/pubsublite/cloudpubsub/internal/publisher_impl.py
@@ -35,7 +35,7 @@ def __init__(self, underlying: AsyncSinglePublisher):
 
     def publish(
         self, data: bytes, ordering_key: str = "", **attrs: Mapping[str, str]
-    ) -> Future:
+    ) -> "Future[str]":
         return self._managed_loop.submit(
             self._underlying.publish(data=data, ordering_key=ordering_key, **attrs)
         )
diff --git a/google/cloud/pubsublite/cloudpubsub/publisher_client.py b/google/cloud/pubsublite/cloudpubsub/publisher_client.py
index 7a984ff9..9ddd4da5 100644
--- a/google/cloud/pubsublite/cloudpubsub/publisher_client.py
+++ b/google/cloud/pubsublite/cloudpubsub/publisher_client.py
@@ -94,7 +94,7 @@ def publish(
         data: bytes,
         ordering_key: str = "",
         **attrs: Mapping[str, str]
-    ) -> Future:
+    ) -> "Future[str]":
         self._require_stared.require_started()
         return self._impl.publish(
             topic=topic, data=data, ordering_key=ordering_key, **attrs
diff --git a/google/cloud/pubsublite/cloudpubsub/publisher_client_interface.py b/google/cloud/pubsublite/cloudpubsub/publisher_client_interface.py
index 6499b407..883a9518 100644
--- a/google/cloud/pubsublite/cloudpubsub/publisher_client_interface.py
+++ b/google/cloud/pubsublite/cloudpubsub/publisher_client_interface.py
@@ -67,7 +67,7 @@ def publish(
         data: bytes,
         ordering_key: str = "",
         **attrs: Mapping[str, str],
-    ) -> Future:
+    ) -> "Future[str]":
         """
     Publish a message.
 
diff --git a/google/cloud/pubsublite/cloudpubsub/subscriber_client.py b/google/cloud/pubsublite/cloudpubsub/subscriber_client.py
index 12ecdae5..eda098fb 100644
--- a/google/cloud/pubsublite/cloudpubsub/subscriber_client.py
+++ b/google/cloud/pubsublite/cloudpubsub/subscriber_client.py
@@ -13,7 +13,7 @@
 # limitations under the License.
 
 from concurrent.futures.thread import ThreadPoolExecutor
-from typing import Optional, Union, Set, AsyncIterator, Callable
+from typing import Optional, Union, Set, AsyncIterator
 
 from google.api_core.client_options import ClientOptions
 from google.auth.credentials import Credentials
@@ -34,6 +34,7 @@
 from google.cloud.pubsublite.cloudpubsub.subscriber_client_interface import (
     SubscriberClientInterface,
     AsyncSubscriberClientInterface,
+    MessageCallback,
 )
 from google.cloud.pubsublite.internal.constructable_from_service_account import (
     ConstructableFromServiceAccount,
@@ -99,7 +100,7 @@ def __init__(
     def subscribe(
         self,
         subscription: Union[SubscriptionPath, str],
-        callback: Callable,  # TODO(dpcollins): Change to MessageCallback,
+        callback: MessageCallback,
         per_partition_flow_control_settings: FlowControlSettings,
         fixed_partitions: Optional[Set[Partition]] = None,
     ) -> StreamingPullFuture:
diff --git a/google/cloud/pubsublite/cloudpubsub/subscriber_client_interface.py b/google/cloud/pubsublite/cloudpubsub/subscriber_client_interface.py
index e9e43113..8dd23506 100644
--- a/google/cloud/pubsublite/cloudpubsub/subscriber_client_interface.py
+++ b/google/cloud/pubsublite/cloudpubsub/subscriber_client_interface.py
@@ -81,7 +81,7 @@ class SubscriberClientInterface(ContextManager):
     def subscribe(
         self,
         subscription: Union[SubscriptionPath, str],
-        callback: Callable,  # TODO(dpcollins): Change to MessageCallback,
+        callback: MessageCallback,
         per_partition_flow_control_settings: FlowControlSettings,
         fixed_partitions: Optional[Set[Partition]] = None,
     ) -> StreamingPullFuture:
diff --git a/setup.py b/setup.py
index ff939886..14a34701 100644
--- a/setup.py
+++ b/setup.py
@@ -29,7 +29,7 @@
 
 dependencies = [
     "google-cloud-pubsub >= 2.1.0, <3.0.0dev",
-    "overrides>=2.0.0, <7.0.0",
+    "overrides>=6.0.1, <7.0.0",
 ]
 
 setuptools.setup(