AU main type update and backward compatibility

Hello devs,

we’ve recently updated one of our plug-in in order to support the MIDI input functionality and in order to be able to use a MIDI in Logic, we had to change the plug-in category from kAudioUnitType_Effect to kAudioUnitType_MusicEffect.
Now everything works as expected but this seems to have the side effect of breaking backward compatibility with previously saved sessions, at least in Logic.
Basically, the updated version is being validated and recognized correctly, you can add a new instance of it but if you open a saved session were the previous version was used (the one with kAudioUnitType_Effect type), Logic says the plug-in cannot be found in the system.

I’m probably out of luck here, but it’s worth a try to ask: is it possible to maintain backward compatibility when changing the AU category?

Thanks in advance,