ClusterJUserException The property is not a member (no replies)

Here there I'm trying to execute a Query with the ClusterJ java api.
When I try to create a Predicate with the following code.
Predicate execIdSellP = er.get("execid_sell").equal(er.param("execid_sellP"));
The following exception is thrown at runtime.
com.mysql.clusterj.ClusterJUserException: The property execid_sell is not a member of com.euroccp.tps.entities.cluster.interfaces.ClearedGrosstradeInterface.
While my interface contains the column like below
@Column(name = "execid_sell")
public String getExecidSell();
public void setExecidSell(String execidSell);

and the column in the database is called execid_sell as well.
When inserting a record via the same interface no problems occur.
Anybody any idea what's wrong ?