Can't filter by Page

I have created a partial which creates a list of pages. I am using len to determine how many pages are in the filter. I would like to exclude the Current Page.

This should look like:

{{ $range := where .Site.RegularPages "Page" "ne" .Page }}

However, this shows nothing when I do that. The only way I’ve found to make this work is by using .File.UniqueID or .Permalink. Why can’t you use the Page variable in a filter?