diff --git a/app/controllers/stockit_controller.rb b/app/controllers/stockit_controller.rb
index a20e16b2..b9a82b65 100644
--- a/app/controllers/stockit_controller.rb
+++ b/app/controllers/stockit_controller.rb
@@ -4,16 +4,16 @@ class StockitController < ApplicationController
     @stock_articles = StockArticle.undeleted.includes(:supplier, :article_category).
         order('suppliers.name, article_categories.name, articles.name')
   end
-  
+
   def index_on_stock_article_create # See publish/subscribe design pattern in /doc.
     @stock_article = StockArticle.find(params[:id])
-    
+
     render :layout => false
   end
 
   def index_on_stock_article_update # See publish/subscribe design pattern in /doc.
     @stock_article = StockArticle.find(params[:id])
-    
+
     render :layout => false
   end
 
@@ -24,43 +24,41 @@ class StockitController < ApplicationController
 
     render :layout => false
   end
-  
+
   # (2) StockArticle as template
   def copy
     @stock_article = StockArticle.find(params[:stock_article_id]).dup
-    
+
     render :layout => false
   end
-  
+
   # (3) non-stock Article as template
   def derive
     @stock_article = Article.find(params[:old_article_id]).becomes(StockArticle).dup
-    
+
     render :layout => false
   end
 
   def create
-    @stock_article = StockArticle.new(params[:stock_article])
-    if @stock_article.valid? && @stock_article.save
-      render :layout => false
-    else
-      render :action => 'new', :layout => false
-    end
+    @stock_article = StockArticle.new({quantity: 0}.merge(params[:stock_article]))
+    @stock_article.save!
+    render :layout => false
+  rescue ActiveRecord::RecordInvalid
+    render :action => 'new', :layout => false
   end
 
   def edit
     @stock_article = StockArticle.find(params[:id])
-    
+
     render :layout => false
   end
 
   def update
     @stock_article = StockArticle.find(params[:id])
-    if @stock_article.update_attributes(params[:stock_article])
-      render :layout => false
-    else
-      render :action => 'edit', :layout => false
-    end
+    @stock_article.update_attributes!(params[:stock_article])
+    render :layout => false
+  rescue ActiveRecord::RecordInvalid
+    render :action => 'edit', :layout => false
   end
 
   def show
@@ -70,7 +68,7 @@ class StockitController < ApplicationController
 
   def show_on_stock_article_update # See publish/subscribe design pattern in /doc.
     @stock_article = StockArticle.find(params[:id])
-    
+
     render :layout => false
   end
 
diff --git a/app/models/stock_article.rb b/app/models/stock_article.rb
index 27fc563c..7837f7c5 100644
--- a/app/models/stock_article.rb
+++ b/app/models/stock_article.rb
@@ -5,6 +5,8 @@ class StockArticle < Article
 
   scope :available, -> { undeleted.where('quantity > 0') }
 
+  validates :quantity, presence: true, numericality: {greater_than_or_equal_to: 0}
+
   before_destroy :check_quantity
 
   # Update the quantity of items in stock
@@ -46,4 +48,3 @@ class StockArticle < Article
     true
   end
 end
-