ORA-01920: user name ‘PERFSTAT’ conflicts with another user or role name

SQL> @?/rdbms/admin/spcreate.sql

Choose the PERFSTAT user's password
-----------------------------------
Not specifying a password will result in the installation FAILING

Enter value for perfstat_password: oracle
oracle


Choose the Default tablespace for the PERFSTAT user
---------------------------------------------------
Below is the list of online tablespaces in this database which can
store user data.  Specifying the SYSTEM tablespace for the user's
default tablespace will result in the installation FAILING, as
using SYSTEM for performance data is not supported.

Choose the PERFSTAT users's default tablespace.  This is the tablespace
in which the STATSPACK tables and indexes will be created.

TABLESPACE_NAME                CONTENTS  STATSPACK DEFAULT TABLESPACE
------------------------------ --------- ----------------------------
EXAMPLE                        PERMANENT
SYSAUX                         PERMANENT *
USERS                          PERMANENT

Pressing <return> will result in STATSPACK's recommended default
tablespace (identified by *) being used.

Enter value for default_tablespace:

Using tablespace SYSAUX as PERFSTAT default tablespace.


Choose the Temporary tablespace for the PERFSTAT user
-----------------------------------------------------
Below is the list of online tablespaces in this database which can
store temporary data (e.g. for sort workareas).  Specifying the SYSTEM
tablespace for the user's temporary tablespace will result in the
installation FAILING, as using SYSTEM for workareas is not supported.

Choose the PERFSTAT user's Temporary tablespace.

TABLESPACE_NAME                CONTENTS  DB DEFAULT TEMP TABLESPACE
------------------------------ --------- --------------------------
TEMP                           TEMPORARY *

Pressing <return> will result in the database's default Temporary
tablespace (identified by *) being used.

Enter value for temporary_tablespace:

Using tablespace TEMP as PERFSTAT temporary tablespace.


... Creating PERFSTAT user
create user perfstat
            *
ERROR at line 1:
ORA-01920: user name 'PERFSTAT' conflicts with another user or role name

SQL> @?/rdbms/admin/spdrop.sql
Dropping old versions (if any)