diff --git a/sdk/communication/azure-communication-chat/azure/communication/chat/_communication_identifier_serializer.py b/sdk/communication/azure-communication-chat/azure/communication/chat/_communication_identifier_serializer.py
index 6b08da1d07ea..188dbe85ec27 100644
--- a/sdk/communication/azure-communication-chat/azure/communication/chat/_communication_identifier_serializer.py
+++ b/sdk/communication/azure-communication-chat/azure/communication/chat/_communication_identifier_serializer.py
@@ -28,7 +28,7 @@ def serialize_identifier(identifier):
     :rtype: ~azure.communication.chat._generated.models.CommunicationIdentifierModel
     """
     try:
-        request_model = {"raw_id": identifier.raw_id}
+        request_model: Dict[str, Any] = {"raw_id": identifier.raw_id}
 
         if identifier.kind and identifier.kind != CommunicationIdentifierKind.UNKNOWN:
             request_model[identifier.kind] = dict(identifier.properties)
@@ -52,7 +52,7 @@ def deserialize_identifier(identifier_model):
     raw_id = identifier_model.raw_id
 
     if identifier_model.communication_user:
-        return CommunicationUserIdentifier(raw_id, raw_id=raw_id)
+        return CommunicationUserIdentifier(raw_id or "", raw_id=raw_id)
     if identifier_model.phone_number:
         return PhoneNumberIdentifier(identifier_model.phone_number.value, raw_id=raw_id)
     if identifier_model.microsoft_teams_user:
@@ -62,4 +62,4 @@ def deserialize_identifier(identifier_model):
             is_anonymous=identifier_model.microsoft_teams_user.is_anonymous,
             cloud=identifier_model.microsoft_teams_user.cloud,
         )
-    return UnknownIdentifier(raw_id)
+    return UnknownIdentifier(raw_id or "")
diff --git a/sdk/communication/azure-communication-chat/azure/communication/chat/_utils.py b/sdk/communication/azure-communication-chat/azure/communication/chat/_utils.py
index c4dc8b52b098..197e51ccd6de 100644
--- a/sdk/communication/azure-communication-chat/azure/communication/chat/_utils.py
+++ b/sdk/communication/azure-communication-chat/azure/communication/chat/_utils.py
@@ -4,6 +4,12 @@
 # license information.
 # --------------------------------------------------------------------------
 
+from typing import List, Tuple, Dict, Optional, TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from ._models import ChatParticipant
+    from ._generated.models import ChatError
+
 
 def _to_utc_datetime(value):
     return value.strftime("%Y-%m-%dT%H:%M:%SZ")
@@ -24,7 +30,7 @@ class CommunicationErrorResponseConverter(object):
 
     @classmethod
     def convert(cls, participants, chat_errors):
-        # type: (...) -> list[(ChatThreadParticipant, ChatError)]
+        # type: (List[ChatParticipant], Optional[List[ChatError]]) -> List[Tuple[Optional[ChatParticipant], ChatError]]
         """
         Util function to convert AddChatParticipantsResult.
 
@@ -41,12 +47,12 @@ def convert(cls, participants, chat_errors):
         """
 
         def create_dict(participants):
-            # type: (...) -> Dict(str, ChatThreadParticipant)
+            # type: (List[ChatParticipant]) -> Dict[str, ChatParticipant]
             """
             Create dictionary of id -> ChatParticipant
 
-            :param list participants: list of ChatThreadParticipant
-            :return: Dictionary of id -> ChatThreadParticipant
+            :param list participants: list of ChatParticipant
+            :return: Dictionary of id -> ChatParticipant
             :rtype: dict
             """
             result = {}
@@ -56,11 +62,13 @@ def create_dict(participants):
 
         _thread_participants_dict = create_dict(participants=participants)
 
-        failed_chat_thread_participants = []
+        failed_chat_thread_participants: List[Tuple[Optional["ChatParticipant"], "ChatError"]] = []
 
         if chat_errors is not None:
             for chat_error in chat_errors:
-                _thread_participant = _thread_participants_dict.get(chat_error.target)
-                failed_chat_thread_participants.append((_thread_participant, chat_error))
+                target = chat_error.target
+                if target is not None:
+                    _thread_participant = _thread_participants_dict.get(target)
+                    failed_chat_thread_participants.append((_thread_participant, chat_error))
 
         return failed_chat_thread_participants
diff --git a/sdk/communication/azure-communication-chat/pyproject.toml b/sdk/communication/azure-communication-chat/pyproject.toml
index 05ee5668ed6a..343877d67195 100644
--- a/sdk/communication/azure-communication-chat/pyproject.toml
+++ b/sdk/communication/azure-communication-chat/pyproject.toml
@@ -1,4 +1,4 @@
 [tool.azure-sdk-build]
-mypy = false
+mypy = true
 pyright = false
 type_check_samples = false