Using Messenger with a basic message object, it first didn't work.
I had to add this to my config/services.yaml file:

services:
    Symfony\Component\Serializer\Normalizer\PropertyNormalizer:
        tags: [serializer.normalizer]

It was preceded by some WTF moments because the error felt unrelated.
Did that happen to others? I feel like this should work by default: create a message class and that's enough: it gets through the bus. That wasn't my experience for now.
WDYT?