unable to use "tags" in global scope

i have .gitlab-ci.yml where all jobs use dind image. so i define the image: in global scope:

image: dind

but dind runner requires --privileged flag, so i need also to pick runner, which can be acomplised by tags

image: dind
tags:
  - dind

however the yml doesn't even parse. the validator on /ci/lint url just gives very brief message:

Status: syntax is incorrect 
Error: Undefined error

i believe global tags is not supported altho the documentation mentions tags only in one place, under jobs: https://docs.gitlab.com/ce/ci/yaml/README.html#tags

having it in global scope helps avoid duplication, currently i think i have to look how to use templates, which makes the config file a bit less readable which is not good either.