NHibernate Oracle CLOB is very slow

I have NHibernate mapping on some tables in our Oracle 11g database, one of the tables contains a CLOB column. If you try to query about 10,000 rows of data, the query is executed forever. When querying a subset of only 200 rows, the query took about 3 minutes. Mathematically, this means that it will take 2.5 hours to query 10,000 rows.

If I remove the CLOB column from NHibernate mapping, the same query takes ~ 3 seconds for 200 rows and ~ 2 minutes for 10,000 rows.

Is this just one issue "by design", either with the Oracle driver or how does NHibernate handle CLOBs?