Using nameservice leads to 'BAD QUERY' for simple query

[graue70]

PREFIX wdt: <http://www.wikidata.org/prop/direct/>
SELECT ?n WHERE {
  ?s wdt:P734 ?n .
}

The query works fine without the nameservice (3M results). With the nameservice, it yields to the following error:

Exception: BAD QUERY (Could not find a suitable execution tree. Likely cause: Queries that require joins of the full index with itself are not supported at the moment.; in ../src/engine/QueryPlanner.cpp, line 2292, function std::vector > QueryPlanner::fillDpTab(const QueryPlanner::TripleGraph&, const std::vector&, const std::vector >&))