embedded sql error

I am attempting to update one file CLPADJRPT (Only selected fields), from
another file ADJDUE (again only selected fields) where two fields match,
these are unique so its always a one to one comparison.

I'm getting a -206 error but I'm not quite sure why.

Here is the code:

0033.47 Exec Sql
0033.48 Update ClpAdjRpt as a
0033.49 Set a.xAjdFnd = b.AjdFnd, a.xajdAmd = b.AjdAmd,
0033.50 a.xAjdAmp = b.AjdAmp, a.xAjdBal = b.AjdBal,
0033.51 a.xAjdTyp = b.AjdTyp
0033.52 Where exists
0033.53 (Select b.ajdfnd, b.ajdamd, b.ajdamp, b.ajdbal,
0033.54 b.ajdtyp
0033.55 from AdjDue as b
0033.56 Where
0033.57 b.ajdrcl = a.xwarcl and b.ajdrln = a.xwarln);

When I attempted to run this via interactive SQL it bombs on the ajdfnd
field...

Any idea what I'm doing wrong here?