When debugging with jest values are displayed as undefined while they have values

I'm wondering why some values are displayed as `undefined` when suspending at a breakpoint while they seem to have values. It seems to happen when accessing global variables from another module:

export let list: string[] = [];

export const setList = (val: string[]) => {
  list = val;
};

with this test:

import { list, setList } from './testdummy';

describe('modify global var from other module', () => {
  it('should modify the global variable', () => {
    setList(['hello, world']);
    expect(list).toHaveLength(1); // success
    expect(list[0]).toBe('hello, world'); // success
  });
});

Everything works fine, but when I set a breakpoint and peek at the value, it's undefined:

Any idea what that might cause that behavior? Thank you!