Oracle Database Express Edition (XE)

I set MAX_STRING_SIZE from STANDARD to EXTENDED in UPGRADE mode.
I checked it with this command:

SELECT * FROM v$parameter WHERE name = 'max_string_size';

..and here is the result in multirows format:

NAME                    max_string_size
VALUE                   EXTENDED
DISPLAY_VALUE           EXTENDED
DEFAULT_VALUE           STANDARD
ISDEFAULT               FALSE
ISSES_MODIFIABLE        FALSE
ISSYS_MODIFIABLE        IMMEDIATE
ISPDB_MODIFIABLE        TRUE
ISINSTANCE_MODIFIABLE   FALSE
ISMODIFIED              FALSE
ISADJUSTED              FALSE
ISDEPRECATED            FALSE
ISBASIC                 FALSE
DESCRIPTION             controls maximum size of VARCHAR2, NVARCHAR2, and RAW types in SQL

I would like to use COLLATE BINARY_CI in a CREATE TABLE and I have the following error message:

CREATE TABLE sample_table 
  (
       sample_column VARCHAR2(50) COLLATE BINARY_CI
  )

ORA-43929: Collation cannot be specified if parameter MAX_STRING_SIZE=STANDARD is set.
Can you help me what is the problem?
Thank you in advance.