diff --git a/app/models/spree/product_decorator.rb b/app/models/spree/product_decorator.rb
index e61f06ee37..d5ccd13dc7 100644
--- a/app/models/spree/product_decorator.rb
+++ b/app/models/spree/product_decorator.rb
@@ -128,6 +128,14 @@ Spree::Product.class_eval do
 
   # -- Methods
 
+  def on_hand
+    if has_variants?
+      variants.map(&:on_hand).reduce(:+)
+    else
+      master.on_hand
+    end
+  end
+
   # Called by Spree::Product::duplicate before saving.
   def duplicate_extra(parent)
     # Spree sets the SKU to "COPY OF #{parent sku}".
diff --git a/app/serializers/api/admin/product_serializer.rb b/app/serializers/api/admin/product_serializer.rb
index 8af5701b94..c7760822d7 100644
--- a/app/serializers/api/admin/product_serializer.rb
+++ b/app/serializers/api/admin/product_serializer.rb
@@ -1,5 +1,5 @@
 class Api::Admin::ProductSerializer < ActiveModel::Serializer
-  attributes :id, :name, :sku, :variant_unit, :variant_unit_scale, :variant_unit_name, :on_demand, :inherits_properties
+  attributes :id, :name, :sku, :variant_unit, :variant_unit_scale, :variant_unit_name, :inherits_properties
 
   attributes :on_hand, :price, :available_on, :permalink_live, :tax_category_id, :import_date, :image_url, :thumb_url
 
diff --git a/app/serializers/api/product_serializer.rb b/app/serializers/api/product_serializer.rb
index 27ea6c5ed4..9f2726cdd7 100644
--- a/app/serializers/api/product_serializer.rb
+++ b/app/serializers/api/product_serializer.rb
@@ -4,7 +4,7 @@ class Api::ProductSerializer < ActiveModel::Serializer
   # TODO
   # Prices can't be cached? How?
   def serializable_hash
-    cached_serializer_hash.merge uncached_serializer_hash
+    cached_serializer_hash.merge(uncached_serializer_hash)
   end
 
   private
@@ -36,7 +36,7 @@ class Api::CachedProductSerializer < ActiveModel::Serializer
   include ActionView::Helpers::SanitizeHelper
 
   attributes :id, :name, :permalink, :meta_keywords
-  attributes :on_demand, :group_buy, :notes, :description, :description_html
+  attributes :group_buy, :notes, :description, :description_html
   attributes :properties_with_values
 
   has_many :variants, serializer: Api::VariantSerializer
diff --git a/spec/models/spree/product_spec.rb b/spec/models/spree/product_spec.rb
index 16f045b03c..76a69d7747 100644
--- a/spec/models/spree/product_spec.rb
+++ b/spec/models/spree/product_spec.rb
@@ -542,7 +542,6 @@ module Spree
       end
     end
 
-
     describe "variant units" do
       context "when the product already has a variant unit set (and all required option types exist)" do
         let!(:p) { create(:simple_product,
@@ -713,6 +712,26 @@ module Spree
         e.variants(true).should be_empty
       end
     end
+
+    describe '#on_hand' do
+      let(:product) { create(:product) }
+
+      context 'when the product has variants' do
+        before { create(:variant, product: product) }
+
+        it 'returns the sum of the on_hand of its variants' do
+          expect(product.on_hand).to eq(Float::INFINITY)
+        end
+      end
+
+      context 'when the product has no variants' do
+        before { product.variants.destroy_all }
+
+        it 'returns the on_hand of the master' do
+          expect(product.on_hand).to eq(product.master.on_hand)
+        end
+      end
+    end
   end
 
   describe "product import" do
diff --git a/spec/serializers/api/admin/product_serializer_spec.rb b/spec/serializers/api/admin/product_serializer_spec.rb
new file mode 100644
index 0000000000..1946735d5e
--- /dev/null
+++ b/spec/serializers/api/admin/product_serializer_spec.rb
@@ -0,0 +1,10 @@
+require 'spec_helper'
+
+describe Api::Admin::ProductSerializer do
+  let(:product) { create(:simple_product) }
+  let(:serializer) { described_class.new(product) }
+
+  it "serializes a product" do
+    expect(serializer.to_json).to match(product.name)
+  end
+end
diff --git a/spec/serializers/spree/product_serializer_spec.rb b/spec/serializers/spree/product_serializer_spec.rb
deleted file mode 100644
index ab6883f9c5..0000000000
--- a/spec/serializers/spree/product_serializer_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-describe Api::Admin::ProductSerializer do
-  let(:product) { create(:simple_product) }
-  it "serializes a product" do
-    serializer = Api::Admin::ProductSerializer.new product
-    serializer.to_json.should match product.name
-  end
-end