Uploading binary or typed array returns undefined on server

[Lamer217]

client.js

Template.itemSubmit.events({
  'input #pictureUpload': async function (event, template) {
    // get the inputted file
    const file = event.target.files[0];
    // get new reader instance
    const reader = new FileReader();

    // fileInfo object is required as the 'file' type is not supported in methods
    const fileInfo = {
      size: file.size,
      type: file.type.split('/')[1],
    };

    reader.onload = function () {
      // as the reader digests the file, turn the result into a uint8array for transmission
      const buffer = new Uint8Array(reader.result);
      // upload the file to the server
      callWithPromise('texts.uploadPictureFile', fileInfo, buffer).then(
        pictureFileName => {
          submitNewPictureTextItem(template, pictureFileName);
        }
      );
    };
    reader.readAsArrayBuffer(file);
  },
});

methods.js

export const uploadPictureFile = new ValidatedMethod({
  name: 'texts.uploadPictureFile',
  validate: null,
  run(fileInfo, fileData) {
    console.log(fileInfo); // { size: 397470, type: 'jpeg' }
    console.log(fileData); // undefined
  },
});

Tried passing binary, array buffer, base64, uint8array. fileData is always undefined. When using standard Meteor method definition – this works as expected. Outputs object and array.