Clash between rails and facets for String exension 'chars'

We've got a problem with the facets gem - i started using facets because
it has some very handy stuff. However, there seems to be a clash with
rails over the extended method String#chars.

in rails, String#chars returns a utf8-safe Chars object:

"hello world!".chars

=> #<ActiveSupport::Multibyte::Chars:0xb657b410 @string="hello world!">

in facets, String#chars returns an array of one-character strings, or at
least that's what the api says:
http://facets.rubyforge.org/doc/index.html

However, when i require 'facets' in my environment.rb, and load the
console, i get the same result as the rails version, ie a Chars object.
Or, at least it looks the same, but it isn't. The difference is
revealed when i try to add a string to the Chars object:

#without facets required

"hello world!".chars[0..4] + "..."

=> #<ActiveSupport::Multibyte::Chars:0xb6652c80 @string="hello ...">

#with facets required

"hello world!".chars[0..4] + "..."

ArgumentError: wrong number of arguments (2 for 1)
  from
/home/max/work/e_learning_resource/branches/bundles/vendor/rails/activerecord/lib/../../activesupport/lib/active_support/multibyte/chars.rb:87:in
`+'
  from
/home/max/work/e_learning_resource/branches/bundles/vendor/rails/activerecord/lib/../../activesupport/lib/active_support/multibyte/chars.rb:87:in
`send'
  from
/home/max/work/e_learning_resource/branches/bundles/vendor/rails/activerecord/lib/../../activesupport/lib/active_support/multibyte/chars.rb:87:in
`method_missing'
  from (irb):3

So, i have two questions...

a) Is there a way to keep facets but to make rails override any methods
with the same name, so i automatically use the rails version of chars
but can still use the other handy facets extensions?

b) How come, with facets required, String#chars is returning a Chars
object when the facets api says it returns an array of 1-character
strings?

any advice/help welcome!
thanks, max