Query-to-map call

I have some problems, when I want to get some informations about specific types of POI from openstreetmaps. I use service query-to-map nad I want to get information about all places with amenity=restaurant tag.

When I call a service with a key and without value, everything works fine and I get a lot of places:

http://toolserver.org/~kolossos/qtm2/featurelist.php?key=amenity&value=&types=points&BBOX=13.5333,50.95,13.9333,51.15

However if I change a call and use a service with nonempty value parameter (like below, where I have key=amenity and value=restaurant) I don't get any result:

http://toolserver.org/~kolossos/qtm2/featurelist.php?key=amenity&value=restaurant&types=points&BBOX=13.5333,50.95,13.9333,51.15

I have also tried with other key and value parameters and it's all the same. There are many restaurants in this area so it's not a problem in map. Any idea what could be wrong and how I can change a call to get information about POI.