diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 6f4322b03..44e3381b7 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -26,6 +26,8 @@ jobs:
 
       - name: Set up Python ${{ matrix.python-version }}
         uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
 
       - name: Set up JDK 17
         uses: actions/setup-java@v4
diff --git a/.python-version b/.python-version
deleted file mode 100644
index e4fba2183..000000000
--- a/.python-version
+++ /dev/null
@@ -1 +0,0 @@
-3.12
diff --git a/packages/smithy-aws-event-stream/src/smithy_aws_event_stream/_private/serializers.py b/packages/smithy-aws-event-stream/src/smithy_aws_event_stream/_private/serializers.py
index a96d38b5c..63e2b0ac1 100644
--- a/packages/smithy-aws-event-stream/src/smithy_aws_event_stream/_private/serializers.py
+++ b/packages/smithy-aws-event-stream/src/smithy_aws_event_stream/_private/serializers.py
@@ -59,10 +59,8 @@ def begin_struct(self, schema: "Schema") -> Iterator[ShapeSerializer]:
         # Note that if we're serializing an operation input or output, it won't be a
         # union at all, so this won't get triggered. Thankfully, that's what we want.
         if schema.shape_type is ShapeType.UNION:
-            try:
-                yield self
-            finally:
-                return
+            yield self
+            return
 
         headers: dict[str, HEADER_VALUE] = {}
 
diff --git a/packages/smithy-core/src/smithy_core/aio/client.py b/packages/smithy-core/src/smithy_core/aio/client.py
index bf27c440c..49e6eab51 100644
--- a/packages/smithy-core/src/smithy_core/aio/client.py
+++ b/packages/smithy-core/src/smithy_core/aio/client.py
@@ -310,7 +310,7 @@ async def _handle_execution[I: SerializeableShape, O: DeserializeableShape](
                 transport_request=interceptor.modify_before_retry_loop(request_context),
             )
 
-            return await self._retry(call, request_context, request_future)
+            return await self._retry(call, request_context, request_future)  # type: ignore[return-value]
         except Exception as e:
             return OutputContext(
                 request=request_context.request,
@@ -325,7 +325,7 @@ async def _retry[I: SerializeableShape, O: DeserializeableShape](
         call: ClientCall[I, O],
         request_context: RequestContext[I, TRequest],
         request_future: Future[RequestContext[I, TRequest]] | None,
-    ) -> OutputContext[I, O, TRequest | None, TResponse | None]:
+    ) -> OutputContext[I, O, TRequest, TResponse | None]:
         if not call.retryable():
             return await self._handle_attempt(call, request_context, request_future)