The following required parameter is missing: [IN]

[Roel Veldhuizen]

I made a form to add a basic person ( firstname, lastname). But
(Although the main functionality of the form works, it's adding a
person) the following errors occur:

The Following Errors Occurred:
The following required parameter is missing: [IN] [createPerson.firstName]
The following required parameter is missing: [IN] [createPerson.lastName]

Why do they occur?

Form:
    <form name="createPerson" type="single" target="createPerson">
        <field name="firstName"><text/></field>
        <field name="lastName"><text/></field>
        <field name="submit"><submit/></field>
    </form>

Widget:
    <screen name="createPerson">
        <section>
            <widgets>
                <decorator-screen name="main-decorator"
location="${parameters.mainDecoratorLocation}">
                    <decorator-section name="body">
                        <include-form name="createPerson"
location="component://crm/widget/CrmForms.xml"/>
                    </decorator-section>
                </decorator-screen>
            </widgets>
        </section>
    </screen>

Thanks in advance,

Roel Veldhuizen