Incremental search don't append wrongly typed characters

[dmgus]

Hi all,

How can I change this behaviour:
 Start incremental search and search for "keyz"
 The "keyz" is displayed in the search echo area and the "key" part in
"keywords" is higlighted
  Type "s"
  "keys" won't be found, the cursor stays on the "keywords" line, search echo
area displays "keyzs", which is not convenient

to that one:
 Start incremental search and search for "keyz"
 The "key" is displayed in the search echo area and the "key" part in "keywords"
is higlighted
 Press s
 "keys" is found and highlited

Although I understand that it's not usual behavior and won't be of help for
everybody, it's still very interesting how to do it. Will appreciate for any
help on this subject.

I've already asked this question on stack overflow though don't have an answer:
http://stackoverflow.com/questions/12099760/emacs-incremental-search-auto-remove-from-the-search-string-the-characters-tha

Thanks,
Dmitry