DV Group by query returns null instead of static value

Environment

• Red Hat JBoss Data Virtualization (DV) 6.3.8
• View transformation:

SELECT  col1, col2, NVL(col3, 'Unspecified') AS col3, NVL(col4, 'Unspecified') AS col4 FROM mytable1

• Selecting from table returns correctly:

SELECT col1, col2, col3, col4 from mytable2
col1    col2        col3        col4
1   John Doe    Unspecified Unspecified
2   Jane Doe    Unspecified Unspecified
3   Jim Smith   Unspecified Unspecified
4   Jane Smith  Unspecified Unspecified

• Static value is ignored with GROUP BY:

SELECT  col1, col2, col3, col4 FROM mytable2 GROUP BY col1,col2,col3,col4
col1    col2        col3        col4
1   John Doe    <null>      <null>
2   Jane Doe    <null>      <null>
3   Jim Smith   <null>      <null>
4   Jane Smith  <null>      <null>