Error with soyOptions.outputDirectory for deleting a soy file

[teppeis]

Closure Templates requires either soyOptions.outputDirectory or soyOptions.outputPathFormat.
clean:soy and build:soy --watch commands work with outputPathFormat but throw errors for deleting soy files with outputDirectory option.

$ duck clean:soy -n
[18:03:17] Clean up soy.js [started]
[18:03:17] Clean up soy.js [failed]
[18:03:17] → Cannot read properties of undefined (reading 'replace')
TypeError: Cannot read properties of undefined (reading 'replace')
    at Object.cleanSoy (node_modules/@cybozu/duck/lib/commands/cleanSoy.js:17:10)
    at node_modules/@cybozu/duck/lib/cli.js:301:45
    at processTicksAndRejections (node:internal/process/task_queues:96:5) {
  context: [Object: null prototype] {}
}