diff --git a/app/controllers/memberships_controller.rb b/app/controllers/memberships_controller.rb
index a722b0d..6c22e4f 100644
--- a/app/controllers/memberships_controller.rb
+++ b/app/controllers/memberships_controller.rb
@@ -30,6 +30,9 @@ class MembershipsController < ApplicationController
         format.html { redirect_to membership_url(@membership), notice: "Membership was successfully created." }
         format.json { render :show, status: :created, location: @membership }
       else
+        # TODO maybe doing something wrong but the variables of new need to be reinitialized here :D
+        @users = User.all
+        @beerclubs = Beerclub.all
         format.html { render :new, status: :unprocessable_entity }
         format.json { render json: @membership.errors, status: :unprocessable_entity }
       end
diff --git a/app/models/membership.rb b/app/models/membership.rb
index 68e730d..69b4aa0 100644
--- a/app/models/membership.rb
+++ b/app/models/membership.rb
@@ -1,4 +1,12 @@
 class Membership < ApplicationRecord
   belongs_to :user
   belongs_to :beerclub
+
+  validate :user_not_in_club
+
+  def user_not_in_club
+    if not Membership.find_by(user_id:user_id, beerclub_id:beerclub_id).nil?
+      errors.add :user_id, "is already in the beerclub"
+    end
+  end
 end
diff --git a/app/views/memberships/_form.html.erb b/app/views/memberships/_form.html.erb
index 9e6ad2c..185b2db 100644
--- a/app/views/memberships/_form.html.erb
+++ b/app/views/memberships/_form.html.erb
@@ -12,8 +12,8 @@
   <% end %>
 
   <div>
-    <%= form.label :user_id, style: "display: block" %>
-    <%= form.select :user_id, options_from_collection_for_select(@users, :id, :username) %>
+      <%= form.label :user_id, style: "display: block" %>
+      <%= form.select :user_id, options_from_collection_for_select(@users, :id, :username) %>
   </div>
 
   <div>