filter=date:2013 doesn't generate a correct elastic query

[MikeYalter]

The query:
/works?query.title=Regional Specialization And Efficiency Of The Agricultural Sector In Greece: The Relationship With Regional Funding Allocation?filter=date:2013&rows=10
generates:
/select params={q=(hl_title:(Technology development for identification of citrus Citrus spp rootstocks based on Sequence Tagged Microsatellite marker filter date 2013) OR hl_subtitle:(Technology development for identification of citrus Citrus spp rootstocks based on Sequence Tagged Microsatellite marker filter date 2013)) &fl=*,score &start=0 &rows=10 &wt=javabin &version=2 &bq=(*:* -type:"Posted Content")}
The filter date 2013 is being included in the actual query and should be a filter parameter.