[firebird-support] Do collation affects index size?

[Fabiano]

Hi all,

create domain d1 varchar(100) character set utf8;
create table t1 (c1 d1, c2 d1);
alter table t1 add unique (c1, c2);

create domain d2 varchar(100) character set utf8 collate unicode_ci_ai;
create table t2 (c1 d2, c2 d2);
alter table t2 add unique (c1, c2);
-- unsuccessful metadata update. key size exceeds implementation restriction 
for index "RDB$2".

Is this error expected?

Firebird 2.5, database page size 4096.