Chat message timestamp undefined when sent but appears on re-entering room

I’m not sure if this is the intended behavior, it but doesn’t seem right. I’m using the API in a custom integration, and when I send a chat message, it’s handled by my listener just fine. However, the timestamp is undefined. Oddly, upon leaving the room and re-entering, the timestamp DOES appear.

Any idea why that might be, or should I report it as an issue?