How to NOT select empty string

We have the following JPQL:

Select distinct sys.ipAddress from SystemLog sys where sys.ipAddress is not null and sys.ipAddress is not empty

And this generates the following mysql statement.

select
    distinct systemlog0_.ipAddress as col_0_0_ 
from
    SystemLog systemlog0_ 
where
    (
        systemlog0_.ipAddress is not null
    ) 
    and (
        exists (
            select
                systemlog0_.id 
            from
                SystemLog systemlog0_
        )
    )

This obviously doesn't work and returns empty string instead of omitting it. However, I am looking for something like this to be generated:

select distinct ipAddress from SystemLog where ipAddress is not null and ipAddress <> '';

However, I can't figure out why our jpa query doesn't generate something simliar like that. Any ideas?