News Redux Reader - having trouble adding comment text after postCommentForArticleId

I am having trouble figuring out how to add the comment text to the byArticleId property after implementing the postCommentForArticleId asynchronous function.

// My postCommentForArticleId implementation
export const postCommentForArticleId = createAsyncThunk(
  "comments/postCommentsForArticleId",
  async ({ articleId, comment }, thunkAPI) => {
    const requestBody = JSON.stringify(comment);
    const response = await fetch(`api/articles/${articleId}/comments`, {
      method: "POST",
      body: requestBody,
    });
    const json = await response.json();
    return json;
  }
);

// ExtraReducer for postCommentForArticleId fulfilled case
[postCommentForArticleId.fulfilled]: (state, action) => {
      if (state.byArticleId[action.payload.articleId]) {
        state.byArticleId[action.payload.articleId].push(/* Need comment text here */);
      } 
      else {
        state.byArticleId[action.payload.articleId] = [/* Need comment text here */];
      }
      state.createCommentIsPending = false;
      state.failedToCreateComment = false;
    }

Normally I would extract what I need from the HTTP response object when working with an extraReducer but the comment text after submitting a comment is nowhere to be found in the HTTP response. Is there another way to access the comment text or a way to include it in the response object?