TypeError: Cannot read properties of undefined (reading 'isInternal')

Hello! I'm trying to create a block tune for one of my apps, here is the code:

class MyBlockTune {
  constructor({ api }) {
    this.api = api;
  }

  isTune() {
    return true
  }

  render() {
    return [
      {
        icon: '<svg>...</svg>',
        label: 'Tune label',
        onActivate: () => { }
      }
    ]
  }
}

After activating it with:

{
  tools: {
    myBlockTune: MyBlockTune,
  },
  tunes: ['myBlockTune'],
}

Editor instance crashes with a following exception thrown:

Which is this line:

After investigating this line a bit with debugger, i can see that this.tunes.myBlockTune is not an instance of anything but is undefined instead.

Editor.js version: 2.28.2