I have a bunch of int key fields in my index and trying to do a simple range search like this: `gender:1 AND height:[120 TO 180]` This should give me male in the height range 120 to 180. But for some reason i get this exception: `At least one range query boundary term must be non-empty term` How would i debug this? Is it just Zend_Search_Lucene being buggy?