Union not supported

[Nudin]

The following SPARQL-Code works with the Webinteface of WDQS but not with wdq ("invalid SPARQL query") – the union seems to be the reason. Is this a bug or is Union not just supported?

SELECT ?floss ?flossLabel ?licenseLabel WHERE {
  {
   ?floss p:P31 ?val.
   ?val v:P31/wdt:P279* wd:Q506883.
  } Union {
   ?floss p:P31 ?val.
   ?val v:P31/wdt:P279* wd:Q341.
  } Union {
   ?floss p:P31 ?val.
   ?val v:P31/wdt:P279* wd:Q1130645.
  }

  ?floss wdt:P275 ?license

   SERVICE wikibase:label {
    bd:serviceParam wikibase:language "en" .
   }
 }