Using Druid "not" Filters

I have the following filters:
{

“filter”: {

“fields”: [

{

“type”: “selector”,

“dimension”: “userid”,

“value”: “xxxxx”

},

{

“field”: {

“type”: “selector”,

“dimension”: “siteid”,

“value”: “yyyy”

},

“type”: “not”

}

],

“type”: “and”

}

}

I am doing a groupby query using these filters which should return all rows matching “userid” == “xxxxx” and all rows Excluding where “siteid” == “yyyy”

The issue is, instead of ignoring rows that match my NOT filter it zeros out the metrics but still returns the rows.

Is there a way to excluded rows that match a not filter so I don’t have to loop over the results and pluck them out after?

Thanks in advance. Using Python by the way.