Unable to specify flags-import: all with remote runs

I have an operation in that looks like this

  operations:
    prepare:
      main: operations.prepare
      flags-import: all
      output-scalars: off

which has a number of different flags specified with argparse in operations/prepare.py. I can run it just fine locally, but when I try run it remote with any flag set I get guild: unsupported flag <flag> for every flag. I can run it remote as long as I don’t set flags. Also, if I specify the flags explicitly in guild.yml like this it works fine:

    prepare:
      main: operations.prepare
      flags:
        <flag1>:
        <flag2>:
      output-scalars: off

Any idea what might be wrong here?

Can you share how the args are specified in your Python script?