Adding a second parameter, even an optional one, means the no-arg method call will fail

anotherParam.groovy

void doSomething(def foo, def newParam = null) {
    println foo
}

void doSomethingAgain(def baz, def newParam) {
    println baz
}

doSomething() // Throws MethodSelectionException
doSomethingAgain('Test') // Throws MissingMethodException