#{index} filter in datatable not work

[nimo22]

I have something like this:

<rich:extendedDataTable value="#{myList}" var="l" rowKeyVar="index">

<rich:column label="Index" sortable="true" sortBy="#{index}" filterBy="#{index}" filterEvent="onkeyup">
 <f:facet name="header">
 <h:outputText value="Index"/>
 </f:facet>
 <h:outputText value ="#{index}"/>
 </rich:column>

..

Unfortunately, the filter of index does not work! When I enter e.g. Index '1' (which exists), the filter returns empty results.