Hrm this isn't helping, so does that mean null is not of type obj then? @Frassle @Zaid-Ajaj I'm pretty sure one of you is going to know what Type constraint mismatch. The type � ''a' �is not compatible with type� 'obj' means :)

This is odd, it runs fine on my machine with dotnet 8 and 9.

Ah ok its a dotnet 10 change, looks like you can just remove the cast and return null directly.