An error occurred while attaching module (Dynamicweb.Frontend.Content)

System.Exception: Root Index is an 'Index' element
   at Dynamicweb.Indexing.IndexHelper.ConvertToIndex(XElement obj, Boolean fillSchema)
   at Dynamicweb.Indexing.IndexService.LoadIndex(String name, Boolean fillSchema)
   at Dynamicweb.Indexing.Querying.Faceting.FacetGroupHelper.PrepareIndexFieldLookup(IFacetGroup facets)
   at Dynamicweb.Indexing.Querying.Faceting.FacetGroupHelper.ConvertToFacets(XElement obj)
   at Dynamicweb.Indexing.Querying.QueryService.LoadFacets(String fileName)
   at Dynamicweb.Ecommerce.Indexing.ProductQueryHelper.LoadFacets(IQuery query, IEnumerable`1 facetGroups)
   at Dynamicweb.Ecommerce.Indexing.ProductQueryHelper.CreateQuerySettings(ProductCatalogSettings settings, IQuery query, PagingHandler pagingHandler, NameValueCollection requestValues)
   at Dynamicweb.Ecommerce.Indexing.ProductQueryHelper.GetQueryAndQuerySettings(ProductCatalogSettings settings, ContentModule contentModule, NameValueCollection requestValues, QuerySettings& querySettings)
   at Dynamicweb.Ecommerce.ProductCatalog.ProductCatalogFrontend.GetModuleContent()
   at Dynamicweb.Frontend.Content.GetModuleOutput(Paragraph paragraph, PageView pageview)