scope causes error in Postgres

The following application working fine with sqlite.

Book model

class Book < ActiveRecord::Base
    attr_accessible :month, :pages, :title, :year, :author_attributes, :publisher_attributes

    belongs_to :author
    belongs_to :publisher

    accepts_nested_attributes_for :author
    accepts_nested_attributes_for :publisher
end

Book controller

class BooksController < ApplicationController
     respond_to(:html)

     expose(:books, :ancestor => [:author, :publisher]) { Book.scoped.paginate(:page => params[:page], :per_page=>params[:per_page])}
     expose(:book)
     # other functions here
end

with postgresql, it gives the following error when I tried to visit http://localhost:3000/books/1

ActiveRecord::StatementInvalid in Books#show

Showing /Users/tunwinnaing/Projects/rails_projects/books/app/views/books/show.html.haml where line #1 raised:

PG::UndefinedParameter: ERROR:  there is no parameter $1    
LINE 1: SELECT COUNT(*) FROM "books"  WHERE "books"."id" = $1    
                                                           ^
: SELECT COUNT(*) FROM "books"  WHERE "books"."id" = $1
Extracted source (around line #1):

1: - provide( :title, "#{book.title} | " )    
2: %h1= book.title    
3: %hr    
4: .row

Background information

• ruby 1.9.3
• rails 3.2.13
• decent_exposure 2.2.0
• will_paginate 3.0.3
• pg 0.16.0
• postgresql 9.x (using postgresapp)

Tried the following

• What is causing PGError: ERROR: there is no parameter $1 in my Rails app - I need will_paginate and couldn't remove the page
• if I removed the Book.scoped.paginate from expose(books), it works but I do not know how to paginate without scope.
• I tried prepared_statement: false in database.yml and conclude that it has nothing to do with this error.

What is the source of problem here? And how could I make it work?