How should I set opt-in in a KMP project?

sourceSets {
    all { languageSettings.optIn("opt.in.Class") }
    commonMain {
        dependecies {
            implementation("dep.that.require.annotation")
        }
    }

}

If I do it that way I get a warning that

opt.in.Class

is unresolved for some source sets.

sourceSets {
    commonMain {
        languageSettings.optIn("opt.in.Class")
        dependecies {
            implementation("dep.that.require.annotation")
        }
    }

}

If I do it this way I get an error that opt in should be applied to all dependent source sets.