Searching on RFC2047 headers

[Ross Boylan]

I'm running Cyrus IMAP 2.2.13 on Debian, and am looking for away to
search on headers that use RFC2047.  I am not able to retrieve anything.
Here's what happens (using imtest)
a06 uid fetch 152840 (BODY[HEADER.FIELDS (subject)])
* 60894 EXISTS
* 1 RECENT
* 59873 FETCH (UID 152840 BODY[HEADER.FIELDS (subject)] {72}
Subject: =?Windows-1251?B?z+7r8/fo8vwgMTEg6vPw8e7iIOHl8e/r4PLt7i4=?=

)
a07 uid search (HEADER SUBJECT "=?Windows-1251?B?z+7r8/fo8vwgMTEg6vPw8e7iIOHl8e/r4PLt7i4=?=")
* SEARCH
a07 OK Completed (0 msgs in 0.140 secs)
a07 uid search charset us-ascii (HEADER SUBJECT "=?Windows-1251?B?z+7r8/fo8vwgMTEg6vPw8e7iIOHl8e/r4PLt7i4=?=")
* SEARCH
a07 OK Completed (0 msgs in 0.140 secs)
a07 uid search charset windows-1251 (HEADER SUBJECT "=?Windows-1251?B?z+7r8/fo8vwgMTEg6vPw8e7iIOHl8e/r4PLt7i4=?=")
a07 NO Unrecognized character set
a07 uid search charset us-ascii (HEADER SUBJECT "z+7r8/fo8vwgMTEg6vPw8e7iIOHl8e/r4PLt7i4")
* SEARCH
a07 OK Completed (0 msgs in 0.150 secs)
a07 uid search charset utf-8 (HEADER SUBJECT "\xcf\xee\xeb\xf3\xf7\xe8\xf2\xfc 11 \xea\xf3\xf0\xf1\xee\xe2 \xe1\xe5\xf1\xef\xeb\xe0\xf2\xed\xee.")
* SEARCH
a07 OK Completed (0 msgs in 0.160 secs)
a07 uid search (HEADER SUBJECT "\xcf\xee\xeb\xf3\xf7\xe8\xf2\xfc 11 \xea\xf3\xf0\xf1\xee\xe2 \xe1\xe5\xf1\xef\xeb\xe0\xf2\xed\xee.")
* SEARCH
a07 OK Completed (0 msgs in 0.130 secs)
a08 uid search (HEADER SUBJECT {63}
+ go ahead
=?Windows-1251?B?z+7r8/fo8vwgMTEg6vPw8e7iIOHl8e/r4PLt7i4=?=

)
* SEARCH
a08 OK Completed (0 msgs in 0.150 secs)

The docs for Cyrus 2.2 do not refer to rfc2047, and so I would expect
the string to be treated as plain text and for any of my initial
searches to work.  Obviously they don't.

I've seen references to cyrus canonicalizing search strings in later
versions
(http://www.cyrusimap.org/docs/cyrus-imapd/2.4.9/internal/internationalization.php)  I'm not sure what the implications of that for this problem are.

Thanks.
Ross