relationTo with globals

Hello all, I'm trying to set up a link field in the admin UI. I used the example from the payload website which provides a dropdown which populates with pages/posts from a few collections.

I have a few pages that I am setting up as globals, and I am looking for a way to include these in the select dropdown. Does anyone have a suggestion?

Here is the relevant field entry:

{
      name: 'reference',
      label: 'Document to link to',
      type: 'relationship',
      relationTo: ['pages', 'posts', 'case-studies'],
      required: true,
      maxDepth: 1,
      admin: {
        condition: (_, siblingData) => siblingData?.type === 'reference',
      },
    },

I have tried adding the global slug in the array, but that does not work.