ORA-30175 on sys_extract_utc unified_audit_trail.event_timestamp in Oracle 12c R1

Question

I can run the following SQL on an Oracle 12c R2:

SQL:

select
sys_extract_utc(event_timestamp) as UTC_Time
from unified_audit_trail

But when the same in 12c R1, I get the following error:

ORA-30175 - invalid type given for an argument

When:

SQL>desc unified_audit_trail ;

in both 12c R1 and R2 there is:

EVENT_TIMESTAMP TIMESTAMP(6) WITH LOCAL TIME ZONE

the column data type is the same, so why is the error on 12c R1 ?

best regards,

Altin