Getting undefined method `errors' for nil:NilClass

I'm doing the Ruby on Rails tutorial at http://guides.rubyonrails.org/getting_started.html

However when I get to "5.11 Adding Some Validation", after adding the error message to display when I try to create a new post from the index view I get

"undefined method `errors' for nil:NilClass"

This is the error line highlighted.

I have already created a new Post in my new action in the controller.

Here is the source

new.html.erb

<h1>New Post</h1>
  <%= form_for :post, url: posts_path do |f| %>
  <% if @post.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@post.errors.count, "error") %> prohibited this post from being saved:</h2>
    <ul>
      <% @post.errors.full_messages.each do |msg| %>
        <li><%= msg %></li>
      <% end %>
    </ul>
    </div>
  <% end %>
  <p>
    <%= f.label :title %><br>
    <%= f.text_field :title %>
  </p>

  <p>
    <%= f.label :text %><br>
    <%= f.text_area :text %>
  </p>

  <p>
    <%= f.submit %>
  </p>
  <% end %>

posts_controller.rb

class PostsController < ApplicationController
def new
    @Post = Post.new
end

def create
    @post = Post.new(post_params)
    if @post.save
        redirect_to @post
    else
        render 'new'
    end
end

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

def index
    @posts = Post.all
end

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

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

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

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

Thanks.