ocaml compile error

[cronburg]

I'm getting this error when I try to do make on ubuntu 14.04 with ocaml version 4.01.0:

ocamlopt.opt -I +camlp5 -I /usr/lib/ocaml/ \
  -I /home/karl/r/pads/padsc/arch/linux.i386-64/lib/xml \
  -pp "camlp5o pa_extend.cmo q_MLast.cmo -mode T " -inline 10 -ccopt -O3 -noassert \
  -c ../hostLanguage.ml
File "../hostLanguage.ml", line 62, characters 11-80:
Error: This expression has type string but an expression was expected of type
     string Ploc.vala

Any idea what's going on? I can't find where Ploc.vala is defined and I'm new to ocaml-style quotation.