rails 4.1.0 bug when finding multiple records while joining a has_many association

gistfile1.rb

rails g model Post
rails g model Comment post_id:integer comment:string

rails c
  p1 = Post.create
  p2 = Post.create
  p1.comments.create(comment: "1")
  p1.comments.create(comment: "2")
  p2.comments.create(comment: "3")
  p2.comments.create(comment: "4")
  p2.comments.create(comment: "5")

2.1.1 :001 > Post.pluck(:id)
   (0.4ms)  SELECT "posts"."id" FROM "posts"
 => [1, 2]

2.1.1 :002 > Comment.all
  Comment Load (0.6ms)  SELECT "comments".* FROM "comments"
 => #<ActiveRecord::Relation [#<Comment id: 1, post_id: 1, comment: "1", created_at: "2014-05-06 22:22:19", updated_at: "2014-05-06 22:22:19">, #<Comment id: 2, post_id: 1, comment: "2", created_at: "2014-05-06 22:22:24", updated_at: "2014-05-06 22:22:24">, #<Comment id: 3, post_id: 2, comment: "3", created_at: "2014-05-06 22:22:46", updated_at: "2014-05-06 22:22:46">, #<Comment id: 4, post_id: 2, comment: "4", created_at: "2014-05-06 22:22:49", updated_at: "2014-05-06 22:22:49">, #<Comment id: 5, post_id: 2, comment: "5", created_at: "2014-05-06 22:22:51", updated_at: "2014-05-06 22:22:51">]> 

2.1.1 :003 > Post.first.comments
  Post Load (0.1ms)  SELECT  "posts".* FROM "posts"   ORDER BY "posts"."id" ASC LIMIT 1
  Comment Load (0.1ms)  SELECT "comments".* FROM "comments"  WHERE "comments"."post_id" = ?  [["post_id", 1]]
 => #<ActiveRecord::Associations::CollectionProxy [#<Comment id: 1, post_id: 1, comment: "1", created_at: "2014-05-06 22:22:19", updated_at: "2014-05-06 22:22:19">, #<Comment id: 2, post_id: 1, comment: "2", created_at: "2014-05-06 22:22:24", updated_at: "2014-05-06 22:22:24">]>
 
2.1.1 :010 > Post.joins(:comments).find(1,2)
  Post Load (0.2ms)  SELECT "posts".* FROM "posts" INNER JOIN "comments" ON "comments"."post_id" = "posts"."id" WHERE "posts"."id" IN (1, 2)
ActiveRecord::RecordNotFound: Couldn't find all Posts with 'id': (1, 2) (found 5 results, but was looking for 2)