cache causes error

Version gitlab-python-runner: 12.6.1-0 OS/Arch: Sparc Solaris 11.3

Just upgraded from 12.4.19-0 to 12.6.1-0 and the following cache causes a runner error:

cache:
   paths:
   - .m2/
   key: "${CI_COMMIT_REF_NAME}"

section_end:1615459561:git
[0K
Runner error: job cache stage test does not exist
  File "/opt/python3.9/lib/python3.9/site-packages/GitlabPyRunner/executor.py", line 246, in run
    config = configloader.read(ci_file)
  File "/opt/python3.9/lib/python3.9/site-packages/gitlabemu/configloader.py", line 221, in read
    validate(baseobj)
  File "/opt/python3.9/lib/python3.9/site-packages/gitlabemu/configloader.py", line 149, in validate
    raise ConfigLoaderError("job {} stage {} does not exist".format(name, job["stage"]))```