Wiki_engine: installation problem

Hi,

I am interested in contributing to wiki_engine, but at installation time
I keep having problems at the DB tables creation time.
In the following I report the error message I got and the Rails
environment.

$ rake migrate
(in /home/cix/Research/Plugins/wiki/vendor/plugins/wiki_engine)
NOTICE: CREATE TABLE will create implicit sequence “pages_id_seq” for
“serial” column “pages.id”
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index
“pages_pkey” for table “pages”
NOTICE: CREATE TABLE will create implicit sequence “versions_id_seq”
for “serial” column “versions.id”
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index
“versions_pkey” for table “versions”
NOTICE: CREATE TABLE will create implicit sequence “books_id_seq” for
“serial” column “books.id”
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index
“books_pkey” for table “books”
NOTICE: CREATE TABLE will create implicit sequence “authors_id_seq” for
“serial” column “authors.id”
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index
“authors_pkey” for table “authors”
rake aborted!
uninitialized constant Version
./Rakefile:33

My environment:
Ruby version 1.8.4 (i486-linux)
RubyGems version 0.8.11
Rails version 1.0.0
Active Record version 1.13.2
Action Pack version 1.11.2
Action Web Service version 1.0.0
Action Mailer version 1.1.5
Active Support version 1.2.5
Environment development
Database adapter postgresql