Pointing two relations to same field?

model User {
  id    Int     @default(autoincrement()) @id
  posts Post[]  @relation(name: "rel")
}

model Post {
  id         Int      @default(autoincrement()) @id
  author1    User?    @relation(name: "rel", fields: [author1Id], references: [id])
  author1Id  Int?
  author2    User?    @relation(name: "rel", fields: [author2Id], references: [id])
  author2Id  Int?
}

Error validating model "Post": Ambiguous relation detected. The fields `author1` and `author2` in model `Post` both refer to `User`. Please provide different relation names for them by adding `@relation(<name>).