Tabpanel - cannot get new tab from ontabchange event

[hdu]

When the tab changes, I would like to rerender a seam button based on the new tab selected. However, in the ontabchange event, the current tab is always the old tab not the new one. How can I access the new tab?

<rich:tabPanel id="myTabPanel" valueChangeListener="#{myPage.changeTab}" selectedTab="#{myPage.tab}" switchType="ajax">
            <a4j:support event="ontabchange" reRender="edit"/>
            <rich:tab id="tabInfo" label="info">
                Info section
            </rich:tab>
            <rich:tab id="tabPreferences" label="Preferences">
                Preferences section
            </rich:tab>

</rich:tabPanel>

<s:button id="edit" value="Edit" view="edit.xhtml" disabled="#{not myPage.isEditable()}"/>

@Name ("myPage")
@Scope (ScopeType.CONVERSATION)
public class MyPage implements Serializable {

  private String tab;

  public String getTab() {
        return tab;
  }

  public void setTab(String tab) {

        this.tab = tab;
  }

  public void changeTab(ValueChangeEvent e) {
        setTab((String) e.getNewValue());
  }

  public boolean isEditable() {
        // These tabs have view and edit page combined
        if (tab.equals("tabInfo")) {
            return false;
        }
        return true;

  }
}