Syntax highlighting for Agda does not work

Summary

GitLab does not seem to do syntax highlighting for Agda programs despite correctly recognising them to be written in Agda.

Steps to reproduce

Trivial. See the following section.

Example Project

https://gitlab.com/ayberkt/agda-highlighting-issue/blob/master/Foo.agda

What is the current bug behavior?

Agda programs are displayed without syntax highlighting. I am not entirely sure this is bug behaviour but I would expect GitLab to do syntax highlighting for every program whose language it can recognise. Therefore I decided to classify this as a bug rather than a feature request.

Output of checks

This bug happens on GitLab.com.