infinidb_import_for_batchinsert_delimiter does not accept high ascii values

I set the value of infinidb_import_for_batchinsert_delimiter to 254 in my my.cnf but when I check the value from the server it is 127!

MariaDB [(none)]> select @@infinidb_import_for_batchinsert_delimiter;
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@@infinidb_import_for_batchinsert_delimiter

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127

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MariaDB [(none)]> set infinidb_import_for_batchinsert_delimiter=254;
Query OK, 0 rows affected, 1 warning (0.00 sec)

MariaDB [(none)]> show warnings;
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Level

Code

Message

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Warning

1292

Truncated incorrect infinidb_import_for_batchinsert_ value: '254'

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1 row in set (0.00 sec)