diff --git a/app/models/spree/product_decorator.rb b/app/models/spree/product_decorator.rb
index d136c2b681..fe20fe5194 100644
--- a/app/models/spree/product_decorator.rb
+++ b/app/models/spree/product_decorator.rb
@@ -12,7 +12,7 @@ Spree::Product.class_eval do
   has_many :option_types, through: :product_option_types, dependent: :destroy
 
   belongs_to :supplier, class_name: 'Enterprise', touch: true
-  belongs_to :primary_taxon, class_name: 'Spree::Taxon'
+  belongs_to :primary_taxon, class_name: 'Spree::Taxon', touch: true
 
   delegate_belongs_to :master, :unit_value, :unit_description
   delegate :images_attributes=, :display_as=, to: :master
diff --git a/spec/models/spree/taxon_spec.rb b/spec/models/spree/taxon_spec.rb
index b19f979d99..54a0069da9 100644
--- a/spec/models/spree/taxon_spec.rb
+++ b/spec/models/spree/taxon_spec.rb
@@ -30,11 +30,20 @@ module Spree
     end
 
     describe "touches" do
-      let!(:taxon) { create(:taxon) }
-      let!(:product) { create(:simple_product) }
+      let!(:taxon1) { create(:taxon) }
+      let!(:taxon2) { create(:taxon) }
+      let!(:taxon3) { create(:taxon) }
+      let!(:product) { create(:simple_product, primary_taxon: taxon1, taxons: [taxon1, taxon2]) }
 
-      it "is touched when applied to a product" do
-        expect{ product.taxons << taxon }.to change { taxon.reload.updated_at }
+      it "is touched when a taxon is applied to a product" do
+        expect{ product.taxons << taxon3 }.to change { taxon3.reload.updated_at }
+      end
+
+      it "is touched when assignment of primary_taxon on a product changes" do
+        expect do
+          product.primary_taxon = taxon2
+          product.save
+        end.to change { taxon2.reload.updated_at }
       end
     end
   end