java - Grails HQL (positional params) query for null timestamp -- strange typecast error -

grails domain property: java.sql.timestamp dateinvoiced

postgresql column: date_invoiced timestamp without time zone

my query:

brokerageorder.executequery(     "select count(*) count brokerageorder d d.dateinvoiced ?",[null]) 

error:

caused by: org.postgresql.util.psqlexception: error: operator not exist: timestamp      without time zone = bytea    hint: no operator matches given name , argument type(s). might need add       explicit type casts. position: 133 

question: how fix this? why think null bytea?

thank you, jeff.