opam build error on Debian 6.0 "squeeze"

[David Sheets <sheets@xxxxxxxxxxxx>]

Hello,

On a fresh Debian 6.0 "squeeze" pv xen vps image, I do

$ sudo apt-get install build-essential ocaml ocaml-native-compilers
camlp4-extra git
$ git clone git://github.com/OCamlPro/opam.git
$ cd opam && make

from <https://raw.github.com/mirage/mirage-www/master/tmpl/wiki/install-opam.md>

then I see

make clone
make[1]: Entering directory `/home/sheets/opam'
make -C src_ext
make[2]: Entering directory `/home/sheets/opam/src_ext'
make[2]: Nothing to be done for `all'.
make[2]: Leaving directory `/home/sheets/opam/src_ext'
make[1]: Leaving directory `/home/sheets/opam'
make compile
make[1]: Entering directory `/home/sheets/opam'
./_obuild/unixrun ./boot/ocp-build.boot -init -scan -sanitize
ocp-build: Entering directory `/home/sheets/opam'
Cache: 428 digests loaded
[723.1] BEGIN 'ocamlc.opt' '-c' '-o'
'/home/sheets/opam/_obuild/723/debcudf.cmo' '-for-pack' 'Debian' '-I'
'./_obuild/dose/Debian' '-I' './_obuild/dose' '-I' './src_ext' '-I'
'./_obuild/extlib' '-I' './_obuild/cudf' '-I' './_obuild/graph' '-I'
'./_obuild/re_perl' '-I' '.' '-pp' 'camlp4o Camlp4MacroParser.cmo'
'src_ext/dose/deb/debcudf.ml'
[723.1]   END ocamlc.opt -c -o
/home/sheets/opam/_obuild/723/debcudf.cmo -for-pack Debian -I
./_obuild/dose/Debian -I ./_obuild/dose -I ./src_ext -I
./_obuild/extlib -I ./_obuild/cudf -I ./_obuild/graph -I
./_obuild/re_perl -I . -pp camlp4o Camlp4MacroParser.cmo
src_ext/dose/deb/debcudf.ml
Command stderr:
File "src_ext/dose/deb/debcudf.ml", line 194, characters 13-26:
Error: Unbound value SMap.bindings
[723.1] ERROR in project dose
Error, exception Unix_error(No such file or directory, stat,
_obuild/dose/Debian/debcudf.cmo) in rule_executed
Warning: 380 rules waiting in queue !
2 errors. 1 commands executed, 1 files generated.
Error:
Target _obuild/dose/Debian/debcudf.cmo not built
Error:
[723.1] ocamlc.opt -c -o /home/sheets/opam/_obuild/723/debcudf.cmo
-for-pack Debian -I ./_obuild/dose/Debian -I ./_obuild/dose -I
./src_ext -I ./_obuild/extlib -I ./_obuild/cudf -I ./_obuild/graph -I
./_obuild/re_perl -I . -pp camlp4o Camlp4MacroParser.cmo
src_ext/dose/deb/debcudf.ml
File "src_ext/dose/deb/debcudf.ml", line 194, characters 13-26:
Error: Unbound value SMap.bindings

make[1]: *** [compile] Error 2
make[1]: Leaving directory `/home/sheets/opam'
make: *** [all] Error 2

What am I missing?

Thanks,

David