Hibernate IS TRUE vs = TRUE

Question

I have a request in Hibernate that was working just fine in an older version of hibernate but after upgrading to a more recent one I have an error

org.hibernate.query.SemanticException: A query exception occurred [SELECT count(c) FROM Client c WHERE c.tmp_batch IS TRUE]
line 1:65 no viable alternative at input 'SELECTcount(c)FROMClientcWHEREc.tmp_batchISTRUE'

public Long getClientCount() {
    return getEntityManager().createQuery("SELECT count(c) FROM Client c WHERE c.tmp_batch IS TRUE", Long.class)
        .getResultList()
        .get(0);
}

After testing a few things, I've got a solution for this problem that replace the IS TRUE by = TRUE and now it works fine again:

public Long getClientCount() {
    return getEntityManager().createQuery("SELECT count(c) FROM Client c WHERE c.tmp_batch = TRUE", Long.class)
        .getResultList()
        .get(0);
}

But I'm unable to understand what's the difference between the two that make the first one to version fall in error, can someone explain the difference here ?

For reference, I'm adding the Client class here :

@Entity
@Table(name = "CLIENTS")
@IdClass(ClientId.class)
public class Client {
    @Id
    @Column(name = "TMP_BATCH")
    private boolean tmp_batch;

    ...

    public boolean isTmp_batch() { return this.tmp_batch; }
    public boolean setTmp_batch(boolean tmp_batch) { this.tmp_batch = tmp_batch; }

    ...

}