`@prisma/client@x is not compatible with prisma2@y. Their versions need to be equal.`, generates anyway

```
C:\Users\Jan\Documents\throwaway\1496
λ npx prisma2@alpha generate
⚠️ @prisma/client@2.0.0-preview021 is not compatible with prisma2@2.0.0-alpha.735. Their versions need to be equal.
Generated Prisma Client to .\node_modules\@prisma\client
Done in 13.52s
```

Is this a warning or an error? The further output indicates it generated anyway. Should it do that or should it really fail?