Get a value from selectOneMenu

[pabloGaitan]

I´m trying to get the value "agrupacionEc" of a p:selectOneMenu combobox, but this value is not being captured (it appears null) before the execution of the valueChangeListener method

This is my code.
xhtml
<p:selectOneMenu value="#{userWizard.agrupacionEc}" style="width:100%" onchange="submit()" valueChangeListener="#{userWizard.valueChanged}">
<f:selectItem itemLabel="Select a ..." />
<f:selectItems value="#{userWizard.agrupaciones}" var="agrup" itemLabel="#{agrup}"
itemValue="#{agrup}"/>
</p:selectOneMenu>

Controller
public void valueChanged(ValueChangeEvent event) {
if(agrupacionEc != null){
if(agrupacionEc.equals(EmpresaTipoActividadEconomica.SERVICIOS)){
visible = true;
}

}

Can anyone help me by indicating what is missing? Thank you!