startObservingQuery does not seem to work with prefixes

[erikxiv]

First off - excellent library. Just started playing around, so I might be off on this issue.

To reproduce

1. Create store
2. startObserviceQuery with a SPARQL query that uses PREFIX notation > an update is triggered with no results
3. Add triples matching the query > No update is triggered

This works

1. Create store
2. startObserviceQuery with a SPARQL query that uses full IRIs without prefixes > an update is triggered with no results
3. Add triples matching the query > Update is triggered as expected