ORA-13541 How can I reduce retention-period of AWR - 11.2.0.2

 Last year I ask you how can I reduce the retention-period of AWR - with oracle version 11.1.0.7. You answered me, that the minimum was 8 days. Now I have an oracle instance with version 11.2.0.2 and when I try to reduce the retention-period to 8 days I get again ORA-13541. Was the minimum change to another value? Do you know this value? Could it be that the value change from 8 to 30 days?
And here the error message:
ERROR at line 1:
ORA-13541: system moving window baseline size (2592000) greater than retention
(691200)
ORA-06512: at "SYS.DBMS_WORKLOAD_REPOSITORY", line 174
ORA-06512: at "SYS.DBMS_WORKLOAD_REPOSITORY", line 222