I'm playing around useSWR and its optimistic updates but I've encountered a problem when using it with prisma.
Prisma returns a single object but the useSWR mutate is expecting an array of all entries ( I think? )

Error is:

Argument of type '{ id: string; imie: string; wiek: number; }' is not assignable to parameter of type '{ id: string; imie: string; wiek: number; }[] | Promise<{ id: string; imie: string; wiek: number; }[] | undefined> | MutatorCallback<{ id: string; imie: string; wiek: number; }[]> | undefined'.ts(2345)

girlsActions.tsx

export async function createGirl({ name, age }: { name: string; age: number }) {
  await new Promise((res) => setTimeout(res, 1000));
  return await prisma.dziewczyna.create({
    data: {
      imie: name,
      wiek: age,
    },
  });
}

girls.tsx

"use client";

import useSWR from "swr";
import useSWRMutation from "swr";
import { getGirls, createGirl } from "../actions/girlsActions";

import type { Dziewczyna } from "@/generated";
import { Button } from "@/components/ui/button";

export default function Girls() {
  const { data: girls, mutate } = useSWR<Dziewczyna[]>("getGirls", getGirls);

  if (!girls) return;

  return (
    <div className="flex flex-col gap-2">
      <p>Girls:</p>
      {girls.map((girl) => {
        return (
          <div key={girl.id}>
            {girl.imie} - {girl.wiek}
          </div>
        );
      })}
      <Button
        onClick={() => {
          mutate(await createGirl({ age: 12, name: "julia" }), {
            optimisticData: [...girls, { wiek: 12, imie: "julia", id: "000" }],
          });
        }}
      >
        Create new girl
      </Button>
    </div>
  );
}

Any ideas?