Moving a wiki page does not place page inside parent

Summary

Trying to move a wiki page to be inside an already existing page, as described in the docs, but gitlab creates new directory instead.

Steps to reproduce

1. Create wiki page (named 'Site Admin').
2. Create another wiki page, with title: 'Site Admin/Database Description'.

Alternatively:

1. Create wiki page (named 'Site Admin').
2. Create another wiki page, with title: 'Database Description'.
3. Edit 'Database Description'.
4. Move 'Database Description' to: 'Site Admin/Database Description'.

Example Project

It's a private project: https://gitlab.com/goncalofig/untied-dev

What is the current bug behavior?

A new directory is created, with the root pages with the same names as the pre-existing pages.

What is the expected correct behavior?

New page should be placed inside the pre-existing pages.

Relevant logs and/or screenshots

Output of checks

This bug happens on GitLab.com