Hyphen as blend_char似乎不起作用

Question

MariaDB> select id,name from t where type='B' and name='Foo-Bar';
+----------------+---------+
| item_source_id | name    |
+----------------+---------+
|        2000245 | Foo-Bar |
+----------------+---------+
1 row in set (0.00 sec)

index base_index { # Don't use this directly; it's for inheritance only.
  blend_chars = +, &, U+23, U+22, U+27, -, /
  blend_mode = trim_none, trim_head, trim_tail, trim_both
}
source b_source : base_source {
  sql_query = select id,name from t where type='B'
  sql_field_string = name
}
index b_index_lemma : base_index {
  source = b_source
  path = /path/b_index_lemma
  morphology = lemmatize_en_all
}

SphinxQL> select * from b_index_lemma where match('Foo-Bar');
Empty set (0.00 sec)

其他Sphinx查询有结果，所以问题不是例如索引是空的。然而，连字符形式没有，我喜欢它。我误用blend_chars - 暨 - blend_mode？