diff --git a/azure/__init__.py b/azure/__init__.py
index d378fc67..db7d5de9 100644
--- a/azure/__init__.py
+++ b/azure/__init__.py
@@ -1,3 +1,3 @@
 """Base module for the Python Durable functions."""
 from pkgutil import extend_path
-__path__ = extend_path(__path__, __name__)
+__path__ = extend_path(__path__, __name__)  # type: ignore
diff --git a/azure/durable_functions/models/DurableOrchestrationClient.py b/azure/durable_functions/models/DurableOrchestrationClient.py
index 76554c5f..3f4bb163 100644
--- a/azure/durable_functions/models/DurableOrchestrationClient.py
+++ b/azure/durable_functions/models/DurableOrchestrationClient.py
@@ -440,6 +440,8 @@ async def wait_for_completion_or_create_check_status_response(
                         lambda: self._create_http_response(200, status.to_json()),
                     OrchestrationRuntimeStatus.Failed:
                         lambda: self._create_http_response(500, status.to_json()),
+                    None:
+                        None
                 }
 
                 result = switch_statement.get(status.runtime_status)
@@ -456,6 +458,7 @@ async def wait_for_completion_or_create_check_status_response(
                 await sleep(sleep_time)
             else:
                 return self.create_check_status_response(request, instance_id)
+        return self.create_check_status_response(request, instance_id)
 
     async def signal_entity(self, entityId: EntityId, operation_name: str,
                             operation_input: Optional[Any] = None,
@@ -640,6 +643,7 @@ async def rewind(self,
 
         response = await self._post_async_request(request_url, None)
         status: int = response[0]
+        ex_msg: str = ""
         if status == 200 or status == 202:
             return
         elif status == 404:
@@ -648,6 +652,9 @@ async def rewind(self,
         elif status == 410:
             ex_msg = "The rewind operation is only supported on failed orchestration instances."
             raise Exception(ex_msg)
-        else:
+        elif isinstance(response[1], str):
             ex_msg = response[1]
             raise Exception(ex_msg)
+        else:
+            ex_msg = "Received unexpected payload from the durable-extension: " + str(response)
+            raise Exception(ex_msg)
diff --git a/azure/durable_functions/models/history/HistoryEvent.py b/azure/durable_functions/models/history/HistoryEvent.py
index 84023944..fa6585b1 100644
--- a/azure/durable_functions/models/history/HistoryEvent.py
+++ b/azure/durable_functions/models/history/HistoryEvent.py
@@ -14,6 +14,13 @@ def __init__(self, EventType: HistoryEventType, EventId: int, IsPlayed: bool, Ti
         self._is_played: bool = IsPlayed
         self._timestamp: datetime.datetime = dt_parse(Timestamp)
         self._is_processed: bool = False
+
+        self.Name = None
+        self.InstanceId = None
+        self.TaskScheduledId = None
+        self.Reason = None
+        self.Details = None
+        self.Input = None
         if kwargs is not None:
             for key, value in kwargs.items():
                 self.__setattr__(key, value)
diff --git a/azure/durable_functions/tasks/call_entity.py b/azure/durable_functions/tasks/call_entity.py
index 467e5b63..5d920405 100644
--- a/azure/durable_functions/tasks/call_entity.py
+++ b/azure/durable_functions/tasks/call_entity.py
@@ -51,7 +51,7 @@ def call_entity_task(
     event_raised = None
     if event_sent:
         event_input = None
-        if hasattr(event_sent, "Input"):
+        if hasattr(event_sent, "Input") and event_sent.Input is not None:
             event_input = RequestMessage.from_json(event_sent.Input)
             hist_type = HistoryEventType.EVENT_RAISED
             extra_constraints = {
diff --git a/azure/durable_functions/tasks/task_all.py b/azure/durable_functions/tasks/task_all.py
index 0758ae61..9d19a917 100644
--- a/azure/durable_functions/tasks/task_all.py
+++ b/azure/durable_functions/tasks/task_all.py
@@ -59,7 +59,7 @@ def task_all(tasks: List[Task]):
 
     # Incomplete TaskSets do not have results or end-time
     if not is_completed:
-        results = None
+        results = []
         end_time = None
 
     # Construct TaskSet
diff --git a/azure/durable_functions/tasks/task_utilities.py b/azure/durable_functions/tasks/task_utilities.py
index cfe8bc2c..b0dd0251 100644
--- a/azure/durable_functions/tasks/task_utilities.py
+++ b/azure/durable_functions/tasks/task_utilities.py
@@ -304,14 +304,18 @@ def gen_err_message(counter: int, mid_message: str, found: str, expected: str) -
         # TODO: The HistoryEvent does not necessarily have a name or an instance_id
         #       We should create sub-classes of these types like JS does, to ensure their
         #       precense.
+
+        if event.Name is None:
+            raise ValueError("History Event for suborchestration found with no {Name} field")
+        event_name: str = event.Name
         err_message: str = ""
         if not(event.Name == name):
             mid_message = "a function name of {} instead of the provided function name of {}."
-            err_message = gen_err_message(counter, mid_message, event.Name, name)
+            err_message = gen_err_message(counter, mid_message, event_name, name)
             raise ValueError(err_message)
         if instance_id and not(event.InstanceId == instance_id):
             mid_message = "an instance id of {} instead of the provided instance id of {}."
-            err_message = gen_err_message(counter, mid_message, event.Name, name)
+            err_message = gen_err_message(counter, mid_message, event_name, name)
             raise ValueError(err_message)
 
     return event
diff --git a/noxfile.py b/noxfile.py
index 25632006..cae7ac72 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -16,5 +16,6 @@ def lint(session):
 
 @nox.session(python=["3.7", "3.8"])
 def typecheck(session):
+    session.install("-r", "requirements.txt")
     session.install("mypy")
     session.run("mypy", "./azure/")
\ No newline at end of file