Root package.json in monorepo not checked?

[lautarodragan]

I'm running npm-package-json-lint, version 5.1.0 in a monorepo that has a root package.json and then several projects under a packages directory, each with their own package.json file.

I added a "lint-package-json": "npmPkgJsonLint ." script to the root package.json and ran yarn lint-package-json from the root, but it's only reporting issues with the children package.json files, ignoring the root one.

$ node -v
v14.4.0
$ npm -v
6.14.5
$ yarn -v
1.22.4

$ cat .npmpackagejsonlintrc.json 
{
  "rules": {
    "prefer-absolute-version-dependencies": "error"
  }
}

$ yarn lint-package-json
yarn run v1.22.4
$ npmPkgJsonLint .

./packages/backend/api/package.json
✖ prefer-absolute-version-dependencies - node: dependencies - You are using an invalid version range. Please use absolute versions.
1 error
0 warnings

./packages/backend/serverless/package.json
✖ prefer-absolute-version-dependencies - node: dependencies - You are using an invalid version range. Please use absolute versions.
1 error
0 warnings

./packages/frontend/admin/package.json
✖ prefer-absolute-version-dependencies - node: dependencies - You are using an invalid version range. Please use absolute versions.
1 error
0 warnings

./packages/frontend/catalog/package.json
✖ prefer-absolute-version-dependencies - node: dependencies - You are using an invalid version range. Please use absolute versions.
1 error
0 warnings

./packages/frontend/editor/package.json
✖ prefer-absolute-version-dependencies - node: dependencies - You are using an invalid version range. Please use absolute versions.
1 error
0 warnings

./packages/frontend/figma-plugin/package.json
✖ prefer-absolute-version-dependencies - node: dependencies - You are using an invalid version range. Please use absolute versions.
1 error
0 warnings

./packages/frontend/next-shared/package.json
✖ prefer-absolute-version-dependencies - node: dependencies - You are using an invalid version range. Please use absolute versions.
1 error
0 warnings

Totals
7 errors
0 warnings
0 files ignored
error Command failed with exit code 2.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

Nothing's reported about the root package.json, even though it does contain a few dependencies that use invalid version ranges.

Am I using npm-package-json-lint incorrectly? How do I get it to lint the root package.json?