Hibernate GROUP BY results in syntax error

Question

My Hibernate query is:

SELECT M.uid, P.userUid, COUNT(*) FROM PostXMentionsEntity M JOIN PostsEntity P GROUP BY M.uid, P.userUid ORDER BY COUNT(*) DESC

where PostXMentionsEntity and PostsEntity are Hibernate mapping objects with said attributes (uid and userUid).

The query crashes with this error message:

ERROR: ERROR: syntax error at or near "group"

which implies something is wrong near the 'GROUP' keyword.

The further stack trace is:

Caused by: org.hibernate.exception.SQLGrammarException: could not extract ResultSet
    at org.hibernate.exception.internal.SQLStateConversionDelegate.convert(SQLStateConversionDelegate.java:103)
    at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:42)
    at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:113)
    at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:99)
    at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.extract(ResultSetReturnImpl.java:67)
    at org.hibernate.loader.Loader.getResultSet(Loader.java:2292)
    at org.hibernate.loader.Loader.executeQueryStatement(Loader.java:2050)
    at org.hibernate.loader.Loader.executeQueryStatement(Loader.java:2012)
    at org.hibernate.loader.Loader.doQuery(Loader.java:953)
    at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:354)
    at org.hibernate.loader.Loader.doList(Loader.java:2838)
    at org.hibernate.loader.Loader.doList(Loader.java:2820)
    at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2652)
    at org.hibernate.loader.Loader.list(Loader.java:2647)
    at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:506)
    at org.hibernate.hql.internal.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:396)
    at org.hibernate.engine.query.spi.HQLQueryPlan.performList(HQLQueryPlan.java:219)
    at org.hibernate.internal.SessionImpl.list(SessionImpl.java:1408)
    at org.hibernate.query.internal.AbstractProducedQuery.doList(AbstractProducedQuery.java:1562)
    at org.hibernate.query.internal.AbstractProducedQuery.list(AbstractProducedQuery.java:1530)
    ... 69 more
Caused by: org.postgresql.util.PSQLException: ERROR: syntax error at or near "group"
  Position: 177
    at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2675)
    at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:2365)
    at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:355)
    at org.postgresql.jdbc.PgStatement.executeInternal(PgStatement.java:490)
    at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:408)
    at org.postgresql.jdbc.PgPreparedStatement.executeWithFlags(PgPreparedStatement.java:167)
    at org.postgresql.jdbc.PgPreparedStatement.executeQuery(PgPreparedStatement.java:119)
    at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.extract(ResultSetReturnImpl.java:57)
    ... 84 more

Am I overlooking something in my HQL query? I translated it from SQL (works verified), and somehow it doesn´t like the grouping keyword, however I found that grouping exists in Hibernate.