GitlabCI runners can't pull from the internal registry

Using the following CI definition fails:

test:
  stage: test
  image: gitlab.archlinux.org:5050/hashworks/archlinux-docker:gitlabcitest
  script:
    - echo "foo"

Running with gitlab-runner 13.2.0 (HEAD)
  on runner1.archlinux.org yqAE3nku
Preparing the "docker" executor
Using Docker executor with image gitlab.archlinux.org:5050/hashworks/archlinux-docker:gitlabcitest ...
Authenticating with credentials from job payload (GitLab Registry)
Pulling docker image gitlab.archlinux.org:5050/hashworks/archlinux-docker:gitlabcitest ...
ERROR: Preparation failed: Error: No such image: gitlab.archlinux.org:5050/hashworks/archlinux-docker:gitlabcitest (docker.go:138:0s)

Job: https://gitlab.archlinux.org/hashworks/archlinux-docker/-/jobs/1340

Image exists:

$ ! test -f ~/.docker/config.json
$ docker pull gitlab.archlinux.org:5050/hashworks/archlinux-docker:gitlabcitest
gitlabcitest: Pulling from hashworks/archlinux-docker
a694805c39f2: Extracting  143.1MB/143.1MB
d644b09eac68: Download complete
d6c01c3368d3: Download complete
2f0690535dd6: Download complete
9f459a7f6e0d: Download complete
97d2f7195771: Download complete