`yarn` not found in `node:alpine`

I'm using the node:alpine image in a gitlab-ci build.
Since a few minutes ago I get the following error in gitlab-ci:

$ yarn config set cache-folder .yarn
/bin/sh: eval: line 50: yarn: not found
ERROR: Job failed: exit code 127

My .gitlab-ci.yaml:

build:
  image: node:alpine
  stage: build
  script:
    - yarn config set cache-folder .yarn
    - yarn
    - yarn build