diff --git a/pubsub/google/cloud/pubsub_v1/subscriber/scheduler.py b/pubsub/google/cloud/pubsub_v1/subscriber/scheduler.py
index 94502d48e754..42674c824c64 100644
--- a/pubsub/google/cloud/pubsub_v1/subscriber/scheduler.py
+++ b/pubsub/google/cloud/pubsub_v1/subscriber/scheduler.py
@@ -73,7 +73,7 @@ def _make_default_thread_pool_executor():
     return concurrent.futures.ThreadPoolExecutor(max_workers=10, **executor_kwargs)
 
 
-class ThreadScheduler(object):
+class ThreadScheduler(Scheduler):
     """A thread pool-based scheduler.
 
     This scheduler is useful in typical I/O-bound message processing.
diff --git a/pubsub/tests/unit/pubsub_v1/subscriber/test_scheduler.py b/pubsub/tests/unit/pubsub_v1/subscriber/test_scheduler.py
index 2e1561db022e..774d0d63e2a2 100644
--- a/pubsub/tests/unit/pubsub_v1/subscriber/test_scheduler.py
+++ b/pubsub/tests/unit/pubsub_v1/subscriber/test_scheduler.py
@@ -21,6 +21,10 @@
 from google.cloud.pubsub_v1.subscriber import scheduler
 
 
+def test_subclasses_base_abc():
+    assert issubclass(scheduler.ThreadScheduler, scheduler.Scheduler)
+
+
 def test_constructor_defaults():
     scheduler_ = scheduler.ThreadScheduler()