Unexpected validation failure with decimal properties

[jabr]

I'm seeing an unexpected validation failure with decimal properties. Also, I'm using the release-1.2 branch.

A simple testcase:

class Model
  include DataMapper::Resource
  property :duration, Decimal
end

m = Model.new
m.duration = BigDecimal.new(1.01, 3)
m.save # raises DataMapper::SaveFailureError
m.errors[:duration] # => ["Duration must be a number"]