Case Expression in GROUP BY clause does not support dynamic bind parameters

We are using criteria builder to frame the query, Select clause having CASE expression and same was placed in GROUP BY Clause as well.

Example Query:

SELECT SUM(
CASE
WHEN t1.IND = 1
THEN t0.HRS
ELSE 0
END ),
CASE
WHEN t0.TRANS_DAY_KY >= 20150322
AND t0.TRANS_DAY_KY <= 20150328
THEN 'Wk - 13'
WHEN t0.TRANS_DAY_KY >= 20150329
AND t0.TRANS_DAY_KY <= 20150404
THEN 'Wk - 14'
ELSE NULL
END AS Period

FROM TIME to,NEWTIME t1
WHERE (t0.TRANS_DAY_KY >= 20150322
AND t0.TRANS_DAY_KY <= 20150404)
GROUP BY
CASE
WHEN t0.TRANS_DAY_KY >= 20150322
AND t0.TRANS_DAY_KY <= 20150328
THEN 'Wk - 13'
WHEN t0.TRANS_DAY_KY >= 20150329
AND t0.TRANS_DAY_KY <= 20150404
THEN 'Wk - 14'
ELSE NULL
END

We are using OpenJpa to implement this Query. OpenJPA Implementation for CASE expression is like below.

Case<String> selectCaseForSelections = cb.<String>selectCase();
selectCaseForSelections.when(cb.and(cb.greaterThanOrEqualTo(dayKey, cb.literal(startTime)), cb.lessThanOrEqualTo(dayKey, cb.literal(endTime))), interval.getName());
selections.add(selectCaseForSelections.alias("Period"); // Adding the CASE Expression to SELECT Clause
groupByCols.add(selectCaseForSelections); // Adding the CASE Expression to GROUP BY Clause

Console TRACE Log shows below Query and Exception.

exception is:nested exception is: javax.ejb.EJBException: See nested exception; nested exception is: <openjpa-2.2.3-SNAPSHOT-r422266:1666312M fatal general error> org.apache.openjpa.persistence.PersistenceException: Missing IN or OUT parameter at index:: 120
SELECT SUM( CASE WHEN t1.IND = ? THEN
t0.HRS ELSE 0 END ),
CASE WHEN t0.TRANS_DAY_KY >= ? AND t0.TRANS_DAY_KY <= ? THEN
'Wk - 13' WHEN t0.TRANS_DAY_KY >= ? AND t0.TRANS_DAY_KY <= ?
THEN 'Wk - 14' ELSE NULL END AS Period
FROM TIME to,NEWTIME t1
WHERE (t0.TRANS_DAY_KY >= ?
AND t0.TRANS_DAY_KY <= ?)
GROUP BY
CASE WHEN t0.TRANS_DAY_KY >= ? AND t0.TRANS_DAY_KY <= ? THEN
'Wk - 13' WHEN t0.TRANS_DAY_KY >= ? AND t0.TRANS_DAY_KY <= ?
THEN 'Wk - 14' ELSE NULL END
[params=(int) 1,(long) 20150322, (long) 20150328, (long) 20150329, (long) 20150404,(long) 20150322, (long) 20150404]
[err] at org.apache.openjpa.lib.jdbc.DelegatingPreparedStatement.executeQuery(DelegatingPreparedStatement.java:268)

The Problem i could see is that Bind parameters are not passed to the GROUP BY Clause. Only for SELECT clause they were passed.
Is it the OpenJPA Limitation ? Could someone help me out.

Thanks in advance.