OPC-UA Server - NaN values in complex datatype

We have a complex data type with double values which are set to NaN if not available. Ignition translates complex data types to a json string. We did an upgrade to Ignition 3.8.6 recently and run into an issue:
The NaN lead to a non valid JSON structure like: {"value": NaN} instead of {"value": "NaN"} or {"value:": null}.

Is this expected?