Spot the Prisma relation error?

model OrderDetail {
    id        String @id @default(cuid())
    orderId   String
    address   String
    city      String
    country   String
    postalCode String
    phone     String
    createdAt DateTime @default(now())
    updatedAt DateTime @updatedAt
    order     Order   @relation(fields: [orderId], references: [id], onDelete: Cascade)
}

model Order {
    id          String   @id @default(cuid())
    createdAt   DateTime @default(now())
    updatedAt   DateTime @updatedAt
    user        User     @relation(fields: [userId], references: [id], onDelete: Cascade)
    userId      String   
    orderItems  OrderItem[]
    orderDetails OrderDetail[] // don't want this to be an array
}