Comment voting with acts as votable

I'm trying to implement a voting system to the comments in the posts using Acts as votable gem. At this stage I'm getting this error

ActionController::UrlGenerationError in Posts#show 

followed by -

No route matches {:action=>"upvote", :controller=>"comments", :id=>nil, :post_id=>#<Comment id: 5, post_id: 3, body: "abc", created_at: "2014-01-12 20:18:00", updated_at: "2014-01-12 20:18:00", user_id: 1>, :format=>nil} missing required keys: [:id]. 

I'm pretty weak with routes.

my routes.rb

resources :posts do
  resources :comments do
    member do
      put "like", to: "comments#upvote"
      put "dislike", to: "comments#downvote"
    end
  end
end

comments controller

def upvote
  @post = Post.find(params[:post_id])
  @comment = @post.comments.find(params[:id])
  @comment.liked_by current_user
  redirect_to @post
end

def downvote
  @post = Post.find(params[:post_id])
  @comment = @post.comments.find(params[:id])
  @comment.downvote_from current_user
  redirect_to @post
end

_comment.html.erb

<%= link_to "Upvote", like_post_comment_path(comment), method: :put %>
<%= link_to "Downvote", dislike_post_comment_path(comment), method: :put %>

You should also pass id of the post in like_post_comment_path like like_post_comment_path(post, comment)