Hibernate version: 3.1

"Select case when then else end " statement works fine unless I add another query in the else clause.
Like below:

select p.category, CASE WHEN p.icrossingTaxonomy.icCategoryId is not null THEN 0
else (select count(*) from Products p1 where p.category = p1.category and p1.icrossingTaxonomy.icCategoryId is null )
end as number
from Products p where p.clients.feedId = 5
group by p.category, p.icrossingTaxonomy.icCategoryId

If I replace the query in the else clause by just a number, the query works fine. By adding that query I get the following exception:

org.hibernate.hql.ast.QuerySyntaxException: unexpected AST node: query [ select p.category, CASE WHEN p.icrossingTaxonomy.icCategoryId is not null THEN 0 else (select count(*) from com.icrossing.icfeedsR3.hibernate.mapping.Products p1 where p.category = p1.category and p1.icrossingTaxonomy.icCategoryId is null ) end as number from com.icrossing.icfeedsR3.hibernate.mapping.Products p where p.clients.feedId = 5 group by p.category, p.icrossingTaxonomy.icCategoryId ]
at org.hibernate.hql.ast.ErrorCounter.throwQueryException(ErrorCounter.java:59)
at org.hibernate.hql.ast.QueryTranslatorImpl.analyze(QueryTranslatorImpl.java:221)
at org.hibernate.hql.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:154)
at org.hibernate.hql.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:101)
at org.hibernate.impl.SessionFactoryImpl.getQuery(SessionFactoryImpl.java:473)
at org.hibernate.impl.SessionImpl.getQueries(SessionImpl.java:1032)
at org.hibernate.impl.SessionImpl.list(SessionImpl.java:982)
at org.hibernate.impl.QueryImpl.list(QueryImpl.java:74)
at com.icrossing.icfeedsR3.model.category.LoadCategoriesModel.loadProductCategoriesSelect(LoadCategoriesModel.java:95)
at com.icrossing.icfeedsR3.model.category.LoadCategoriesModel.main(LoadCategoriesModel.java:123)
Caused by: <AST>:0:0: unexpected AST node: query
at org.hibernate.hql.antlr.HqlSqlBaseWalker.expr(HqlSqlBaseWalker.java:1298)
at org.hibernate.hql.antlr.HqlSqlBaseWalker.caseExpr(HqlSqlBaseWalker.java:4633)
at org.hibernate.hql.antlr.HqlSqlBaseWalker.arithmeticExpr(HqlSqlBaseWalker.java:2805)
at org.hibernate.hql.antlr.HqlSqlBaseWalker.selectExpr(HqlSqlBaseWalker.java:1990)
at org.hibernate.hql.antlr.HqlSqlBaseWalker.aliasedSelectExpr(HqlSqlBaseWalker.java:2041)
at org.hibernate.hql.antlr.HqlSqlBaseWalker.selectExprList(HqlSqlBaseWalker.java:1816)
at org.hibernate.hql.antlr.HqlSqlBaseWalker.selectClause(HqlSqlBaseWalker.java:1380)
at org.hibernate.hql.antlr.HqlSqlBaseWalker.query(HqlSqlBaseWalker.java:541)
at org.hibernate.hql.antlr.HqlSqlBaseWalker.selectStatement(HqlSqlBaseWalker.java:269)
at org.hibernate.hql.antlr.HqlSqlBaseWalker.statement(HqlSqlBaseWalker.java:217)
at org.hibernate.hql.ast.QueryTranslatorImpl.analyze(QueryTranslatorImpl.java:214)
... 8 more