Datatable values from Map, sorting is by key, not value

[Jack Lund]

Hello, my code:

   
    <t:dataTable id="customerTable"
            var="customer"
            value="#{testActionBean.customerList}"
        <t:column sortable="true">
             <f:facet name="header">
                 <t:commandSortHeader columnName="customerName" arrow="false" immediate="false">
                     <f:facet name="ascending">
                         <t:graphicImage url="sort-up.gif" align="right" border="0" />
                     </f:facet>
                     <f:facet name="descending">
                         <t:graphicImage url="sort-down.gif"  align="right" border="0" />
                     </f:facet>
                     <h:outputText value="#{msgs['customerName']}" />
                 </t:commandSortHeader>
             </f:facet>
             <h:outputText value="#{testActionBean.customerNameMap[customer.id]}"/>
        </t:column>
    </t:dataTable>
 

The problem is that sorting is based on customer id's, not customer names. The names are displayed properly. Is this a bug or is something wrong with my code?