Maybe error in exiscan

In the "demime" facility. 

I use debian sid (packages exim4 4.34-4, inc. exiscan version 21) with
standard rule:

 deny  message = $found_extension files are not accepted here
      demime = com:exe:vbs:bat:pif:scr

Works fine, exe's file is not accepted. But this rule not working when 
attachment name is: "=?windows-1251?Q?2707=EF=EE=EB=2Eexe?=" (base64)


Content-Type: application/x-msdownload;
 name="=?windows-1251?Q?2707=EF=EE=EB=2Eexe?="
Content-Transfer-Encoding: base64
Content-Disposition: inline;
 filename="=?windows-1251?Q?2707=EF=EE=EB=2Eexe?="

Any ideas?

-- 
 Cezary