Attachment urls not including port number

So I’m trying to use the Docker version of GitLab. Majority of the features appear to work, but I cannot seem to get static assets / attachments to appear correctly. The URLs appear to be missing the port number that is defined in the gitlab.rb external_url?

Here is what I see when I inspect the element:

img src=“http://x.x.x.x/root/Test/uploads/1d5e86f9107f54182bcf54b09189efa5/qlxgrwj.gif” alt=“qlxgrwj”

When I correct the url by adding the missing port, the asset loads correctly. What do I need to set in gitlab for it to attach the port to the generated url?