I have following code:

        <p:panel id="selectDocumentTypePanel">
            <div class="push-20"/>
            <nf:select fieldId="selectDocumentType" label="#{msg['configuration.doc.new.type.document']}">
                <h:selectOneMenu id="selectDocumentType"
                                 value="#{dcNewEditBean.documentConfiguration.type}"
                                 required="true"
                                 requiredMessage="#{of:format1(msg['validation.field.required'], msg['configuration.doc.new.type.document'])}"
                                 styleClass="-width-100 -form-select">
                    <p:ajax event="change" process="@this"
                            update="#{p:component('panel_max_docs')} #{p:component('roles_for_view')}"/>
                    <f:selectItem itemLabel="#{msg['menu.export.tab.checkbox.choose']}" itemValue="#{null}"
                                  noSelectionOption="true"/>
                    <f:selectItems value="#{dcNewEditBean.availableDocumentTypes}" var="documentType"
                                   itemLabel="#{msg[documentType.key]}"/>
                </h:selectOneMenu>
            </nf:select>
        </p:panel>

After selection label menu.export.tab.checkbox.choose it changes on the front to my specified message, but in backend on dcNewEditBean.documentConfiguration.type variable there’s previously choosen value, not null.
Do You know maybe what’s wrong here?
I’m on Primefaces 7