diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5223457d7..9027a0d6c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,7 @@
 # Change log
 
 - [#516](https://github.com/mobilityhouse/ocpp/issues/516) OCPP 2.0.1 add additional security events from v1.3
+- [#537] (https://github.com/mobilityhouse/ocpp/pull/537) Fix DataTransfer data types 
 
 ## 0.23.0 (2023-11-30)
 
diff --git a/ocpp/v201/call.py b/ocpp/v201/call.py
index f97f9a1e1..bff98238b 100644
--- a/ocpp/v201/call.py
+++ b/ocpp/v201/call.py
@@ -90,7 +90,7 @@ class CustomerInformationPayload:
 class DataTransferPayload:
     vendor_id: str
     message_id: Optional[str] = None
-    data: Optional[str] = None
+    data: Optional[Any] = None
     custom_data: Optional[Dict[str, Any]] = None
 
 
diff --git a/ocpp/v201/call_result.py b/ocpp/v201/call_result.py
index 6f3b25f0b..3a59b07a2 100644
--- a/ocpp/v201/call_result.py
+++ b/ocpp/v201/call_result.py
@@ -87,7 +87,7 @@ class CustomerInformationPayload:
 class DataTransferPayload:
     status: str
     status_info: Optional[Dict] = None
-    data: Optional[Dict] = None
+    data: Optional[Any] = None
     custom_data: Optional[Dict[str, Any]] = None