format goal does not auto-intend

[emilpaw]

When setting up the pom.xml like described in the "Formatting as part of the build" section of the usage documentation the code is not auto-intended.
If I instead run
mvn com.github.gantsign.maven:ktlint-maven-plugin:1.9.0:format
the code is intended flawlessly.
Please excuse my ignorance if I just miss configured my pom.xml and it's not an issue with the plugin itself.

Thanks.