Multi-stage dockerfile problem

Summary

Multi-stage builds was introduced in 17.05.0-ce
But building images from such Dockerfile's failed with gitlab-ci.

Steps to reproduce

FROM busybox:musl as builder
RUN touch /file

FROM scratch
COPY --from=builder /file /

image: docker:latest

services:
  - docker:dind

build-master:
  stage: build
  script:
    - docker build --pull -t "$CI_REGISTRY_IMAGE" .
  only:
    - master

Actual behavior

Building error

Expected behavior

Successful building

Relevant logs and/or screenshots

Running with gitlab-ci-multi-runner 9.3.0 (3df822b)
  on docker-auto-scale (4e4528ca)
Using Docker executor with image docker:latest ...
Starting service docker:dind ...
Pulling docker image docker:dind ...
Using docker image docker:dind ID=sha256:5096e5a0cba00693905879b09e24a487dc244b56e8e15349fd5b71b432c6ec9f for docker service...
Waiting for services to be up and running...
Using docker image sha256:0c2e8b57d08cd579accf0db26ced38db97ec48aa9f46b3a140346fe18013bef6 for predefined container...
Pulling docker image docker:latest ...
Using docker image docker:latest ID=sha256:192e3edb771f334fbc2e1941b22a0b3ecd8545a86744ce8fc2fe98a3d5774273 for build container...
Running on runner-4e4528ca-project-3716777-concurrent-0 via runner-4e4528ca-machine-1500422096-9ff86d0e-digital-ocean-2gb...
Cloning repository...
Cloning into '/builds/farwayer/test'...
Checking out 12d30498 as master...
Skipping Git submodules setup
$ docker build --pull -t "$CI_REGISTRY_IMAGE" .
Sending build context to Docker daemon  28.67kB

Step 1/4 : FROM busybox:musl as builder
musl: Pulling from library/busybox
3c549a46cf66: Pulling fs layer
3c549a46cf66: Verifying Checksum
3c549a46cf66: Pull complete
Digest: sha256:2a81301bac2b8bff3cb051bd42ec4540b027b77d118d218c9c512de55d973be8
Status: Downloaded newer image for busybox:musl
 ---> a6a443eecbe9
Step 2/4 : RUN touch /file
 ---> Running in eed370845163
 ---> 8971d634da62
Removing intermediate container eed370845163
Step 3/4 : FROM scratch
 ---> 
Step 4/4 : COPY --from=builder /file /
invalid from flag value builder: repository sha256 not found: does not exist or no pull access
ERROR: Job failed: exit code 1

Environment description

Shared Runners on GitLab.com

Used GitLab Runner version

Running with gitlab-ci-multi-runner 9.3.0 (3df822b)
Using Docker executor with image docker:latest ...