diff --git a/lib/dm-validations.rb b/lib/dm-validations.rb
index 0d20920a..863d6b7b 100644
--- a/lib/dm-validations.rb
+++ b/lib/dm-validations.rb
@@ -235,6 +235,37 @@ def add_validator_to_context(opts, fields, validator_class)
           end
         end
       end
+
+      # Automatically adds a validation to all associations so that validation
+      # on parent models will return false when children are invalid. This
+      # matches the behaviour of #save, which returns false if child models
+      # cannot be saved.
+      #
+      # TODO: Validations are only run on dirty models (which includes new models),
+      # since clean ones are assumed to be valid. This prevents validations
+      # from cascading down to nested child models when not required.
+      def has(cardinality, property, *args)
+        super.tap do
+          next if @disable_auto_validations
+
+          add_validation = lambda do |conditional|
+            validates_with_block property do
+              value = send(property)
+              if conditional[value]
+                [false, "#{property.to_s.titleize} must be valid"]
+              else
+                true
+              end
+            end
+          end
+
+          if cardinality == 1 || (cardinality.is_a?(Range) && cardinality.max == 1)
+            add_validation[lambda {|val| val && val.dirty? && !val.valid? }]
+          else
+            add_validation[lambda {|val| val.loaded? && !val.map(&:valid?).all? }]
+          end
+        end
+      end
     end # module ClassMethods
   end # module Validations
 
diff --git a/spec/fixtures/company.rb b/spec/fixtures/company.rb
index 4c072aad..ace0fc43 100644
--- a/spec/fixtures/company.rb
+++ b/spec/fixtures/company.rb
@@ -60,6 +60,23 @@ class ProductCompany < Company
 
         validates_presence_of :title, :message => "Product company must have a name"
         validates_presence_of :flagship_product
+
+        has n, :products, :child_key => [:company_id]
+        has 1, :profile
+        has 0..1, :alternate_profile, :model => "Profile"
+
+        without_auto_validations do
+          has 0..1, :yet_another_profile, :model => "Profile"
+        end
+      end
+
+      class Profile
+        include DataMapper::Resource
+
+        property :id, Serial
+        belongs_to :product_company
+        property :description, Text, :required => false # Allow NULL values, enforce validation in the app
+        validates_presence_of :description
       end
 
       class Product
diff --git a/spec/integration/datamapper_models/association_validation_spec.rb b/spec/integration/datamapper_models/association_validation_spec.rb
index eab6ddcd..cb478b6c 100644
--- a/spec/integration/datamapper_models/association_validation_spec.rb
+++ b/spec/integration/datamapper_models/association_validation_spec.rb
@@ -24,3 +24,70 @@
     end
   end
 end
+
+describe 'DataMapper::Validations::Fixtures::ProductCompany' do
+  before :all do
+    @model = DataMapper::Validations::Fixtures::ProductCompany.create(:title => "Apple", :flagship_product => "Macintosh")
+  end
+
+  describe 'with no products loaded' do
+    it 'does not load or validate it' do
+      @model.reload
+      @model.valid?
+      @model.products.should_not be_loaded
+    end
+  end
+
+  describe 'with no profile loaded' do
+    it 'does not load or validate it' do
+      pending "Unsure how to test this"
+      @model.reload
+      @model.valid?
+      @model.profile.should_not be_loaded
+    end
+  end
+
+  describe 'with not dirty profile' do
+    before :all do
+      # Force an invalid, yet clean model. This should not happen in real
+      # code, but gives us an easy way to check whether the validations
+      # are getting run on the profile.
+      profile = DataMapper::Validations::Fixtures::Profile.create!(:product_company => @model)
+      @model.reload
+    end
+
+    it_should_behave_like "valid model"
+  end
+
+  describe 'with invalid products' do
+    before :all do
+      @model.products = [DataMapper::Validations::Fixtures::Product.new]
+    end
+
+    it_should_behave_like "invalid model"
+
+    it "has a meaningful error message" do
+      @model.errors.on(:products).should == [ 'Products must be valid' ]
+    end
+  end
+
+  describe 'with invalid profile' do
+    before :all do
+      @model.profile = DataMapper::Validations::Fixtures::Profile.new
+    end
+
+    it_should_behave_like "invalid model"
+
+    it "has a meaningful error message" do
+      @model.errors.on(:profile).should == [ 'Profile must be valid' ]
+    end
+  end
+
+  describe 'with invalid yet_another_profile' do
+    before :all do
+      @model.yet_another_profile = DataMapper::Validations::Fixtures::Profile.new
+    end
+
+    it_should_behave_like "valid model"
+  end
+end