[exim] Expansion issue in 4.86.2

Hi,
maybe there is a (minor?) problem with some specific expansion situations.
Or maybe I'm totally confused ...

I have a expansion expression which works for years and up to exim 4.77
the result in test mode (with -be option) is "false" (as expected).

But when trying 4.86.2 the result is "Failed: missing or misplaced { or }".
I'm fairly sure that the { and } are ok and the result in both versions
should be the same.

  ${lookup{TESTUSER}dbm{/opt/global/cache/passwd.db}
     {${extract{2}{:}{$value}
          {${extract{1}{,}{$value}
              {${if crypteq{TESTPASSWORD}{\{crypt\}$value}{true}{false}}}
          {false}}}
     {false}}}
  {false}}

It all works when the lookup succeeds. The inner extract-crypt-compare work
as expected. But when looking up a dummy value, the result should be "false"
(skipping the inner expressions).

Any ideas ?

Martin