SET BIND OF TIMESTAMP WITH TIME ZONE TO CHAR is not working with UTF8 connection charset

[skopaliks]

FB 4.0.2 windows x64

SQL Script:
CREATE DATABASE 'xnet://d:\fbdata\test.fdb' USER 'SYSDBA' PASSWORD 'masterkey';

RECREATE TABLE a(
t TIMESTAMP WITH TIME ZONE
);

INSERT INTO a VALUES(CURRENT_TIMESTAMP);

SELECT * FROM a;

SET TERM ^;
EXECUTE BLOCK AS
BEGIN
SET BIND OF TIMESTAMP WITH TIME ZONE TO CHAR;
END
^
SET TERM ;^

SELECT * FROM a;
COMMIT;

WIN1250 works fine:
c:\fb\isql.exe -ch WIN1250 -i set_bind_error.sql

UTF8 are failing:
c:\fb\isql.exe -ch UTF8 -i set_bind_error.sql

T

Statement failed, SQLSTATE = 22001
Dynamic SQL Error
-SQL error code = -303
-arithmetic exception, numeric overflow, or string truncation
-string right truncation
-expected length 14, actual 41