Rails no method error since installing devise?

I am not sure that it is even related but since i added devise i am getting a no method error which reads as follows. undefined method `posts' for nil:NilClass This is specifically directed at the following line of code.

@post = current_user.posts.build

I am rather stuck here as i have checked all the obvious and unless i remove the code so it reads

@post = Post.new

I am otherwise unable to add new posts. I have added the full code below. Posts Controller

class PostsController < ApplicationController
before_action :find_post, only: [:show, :edit, :update, :destroy]

def index
    @posts = Post.all.order("created_at DESC")
end

def show
end

def new
    @post = current_user.posts.build
end

def create
    @post = current_user.posts.build(post_params)

    if @post.save
        redirect_to @post
    else
        render 'new'
    end
end

def edit
end

def update
    if @post.update(post_params)
        redirect_to @post
    else
        render 'edit'
    end
end

def destroy
    @post.destroy
    redirect_to root_path
end

private

def find_post
    @post = Post.find(params[:id])
end

def post_params
    params.require(:post).permit(:title, :content)
end
end

Post model`

 class Post < ActiveRecord::Base
    belongs_to :user
 end

User model

class User < ActiveRecord::Base
  # Include default devise modules. Others available are:
  # :confirmable, :lockable, :timeoutable and :omniauthable
  devise :database_authenticatable, :registerable,
         :recoverable, :rememberable, :trackable, :validatable
  has_many :posts
end

new html haml

%h1 New Post

= render 'form'