use highlighting on multivalued fields with positionIncrementGap 0

[Nicolas Franck]

I'm trying to use highlighting on a multivalued text field (analysis not so 
important) ..


  { text: [ "hello", "world" ], id: 1 }

but I want to match across the string boundaries:

  q=text:"hello world"

This works by setting the attribute
positionIncrementGap to 0, but then the hightlighting entry is empty

  "highlighting": { "1" : { "text" : [] } }

Parameters are:

  hl=true
  hl.fl=text
  hl.snippets=50
  hl.fragSize=10000

Any idea why this happens? 
I guess this gap is internal stuff handled by Lucene that Solr doesn't know 
about?
(as for lucene, there are no multivalued fields!)