Graphql upload file shows as empty object

Question

when I'm trying to upload file via Graphql mutation (apollo-angular) with parameter $file: Upload!, the variable value is shown as an empty object in developer tools:

But I'm checking the value of the variable right before the request and the value is correct, it is in fact a File, not an empty object.

import gql from 'graphql-tag';
import { Apollo } from 'apollo-angular';

  this.apollo.mutate(
    {
      mutation: gql`
        ${uploadMutation}
      `,
      variables: {
        companyId,
        file <-- Here the value is correct, it is a File
      },
      context: {
        hasUpload: true,
        useMultipart: true
      }
    },
    'upload'
  );

Code is simplified for the sake of this example.

Is it just developer tools issue, am I doing something wrong or what is the problem please?