Cannot set repository to pull mirror

Summary

In self-hosted GitLab Enterprise Edition 13.5.3-ee, unable to create pull mirror: pull option is greyed out.

Steps to reproduce

Have a self hosted instance with EE license. Create a new repository that is imported by URL from another repository.

Example Project

Self hosted: N/A

What is the current bug behavior?

Navigate to Settings -> Repository, expand Mirroring repositories. Enter URL of remote repository (http://osm.etsi.org/osm/devops.git). Attempt to change Mirror direction, but cannot. Push is shown in grey and cannot be changed.

What is the expected correct behavior?

Able to select mirror direction of Pull.

Relevant logs and/or screenshots

Output of checks

This bug happens on self-hosted GitLab

Results of GitLab environment info

Results of GitLab application Check

Possible fixes