diff --git a/lib/mysql-binuuid/type.rb b/lib/mysql-binuuid/type.rb
index 8273fa6..15e2130 100644
--- a/lib/mysql-binuuid/type.rb
+++ b/lib/mysql-binuuid/type.rb
@@ -12,13 +12,17 @@ def cast(value)
       if value.is_a?(MySQLBinUUID::Type::Data)
         # It could be a Data object, in which case we should add dashes to the
         # string value from there.
-        add_dashes(value.to_s)
-      elsif value.is_a?(String) && value.encoding == Encoding::ASCII_8BIT && strip_dashes(value).length != 32
-        # We cannot unpack something that looks like a UUID, with or without
-        # dashes. Not entirely sure why ActiveRecord does a weird combination of
-        # cast and serialize before anything needs to be saved..
-        undashed_uuid = value.unpack1('H*')
-        add_dashes(undashed_uuid.to_s)
+        add_dashes(value.to_s.downcase)
+      elsif value.is_a?(String)
+        if value.encoding == Encoding::ASCII_8BIT && strip_dashes(value).length != 32
+          # We cannot unpack something that looks like a UUID, with or without
+          # dashes. Not entirely sure why ActiveRecord does a weird combination of
+          # cast and serialize before anything needs to be saved..
+          undashed_uuid = value.unpack1('H*')
+          add_dashes(undashed_uuid.to_s.downcase)
+        else
+          value.downcase
+        end
       else
         super
       end
diff --git a/lib/mysql-binuuid/version.rb b/lib/mysql-binuuid/version.rb
index 36b21fb..82d6a9a 100644
--- a/lib/mysql-binuuid/version.rb
+++ b/lib/mysql-binuuid/version.rb
@@ -1,3 +1,3 @@
 module MySQLBinUUID
-  VERSION = "1.3.0"
+  VERSION = "2.0.0"
 end
diff --git a/test/integration/mysql_integration_test.rb b/test/integration/mysql_integration_test.rb
index de1ce75..23ef1e3 100644
--- a/test/integration/mysql_integration_test.rb
+++ b/test/integration/mysql_integration_test.rb
@@ -4,10 +4,33 @@ class MyUuidModel < ActiveRecord::Base
   attribute :the_uuid, MySQLBinUUID::Type.new
 end
 
+class UuidPkeyModel < ActiveRecord::Base
+  self.abstract_class = true
+
+  attribute :id, MySQLBinUUID::Type.new
+
+  after_initialize :set_id
+
+  private
+
+  def set_id
+    self.id ||= SecureRandom.uuid
+  end
+end
+
 class MyUuidModelWithValidations < MyUuidModel
   validates :the_uuid, uniqueness: true
 end
 
+class UuidParent < UuidPkeyModel
+  has_many :uuid_children
+end
+
+class UuidChild < UuidPkeyModel
+  belongs_to :uuid_parent
+  attribute :uuid_parent_id, MySQLBinUUID::Type.new
+end
+
 class MySQLIntegrationTest < ActiveSupport::TestCase
   def connection
     ActiveRecord::Base.connection
@@ -35,6 +58,9 @@ def db_config
     ActiveRecord::Base.establish_connection(db_config)
     connection.create_table("my_uuid_models")
     connection.add_column("my_uuid_models", "the_uuid", :binary, limit: 16)
+    connection.create_table('uuid_parents', id: 'binary(16)')
+    connection.create_table('uuid_children', id: 'binary(16)')
+    connection.add_columns('uuid_children', 'uuid_parent_id', type: 'binary(16)')
 
     # Uncomment this line to get logging on stdout
     # ActiveRecord::Base.logger = Logger.new(STDOUT)
@@ -122,5 +148,34 @@ class AfterPersistedTest < MySQLIntegrationTest
         MyUuidModel.create!(the_uuid: "40' + x'40")
       end
     end
+
+    test "always downcases the user-supplied value" do
+      @my_model.the_uuid = @sample_uuid.upcase
+      assert_equal @sample_uuid, @my_model.the_uuid
+    end
+
+    test "treats case-only changes as non-dirtying" do
+      @my_model.the_uuid = @sample_uuid.upcase
+      assert_equal false, @my_model.will_save_change_to_the_uuid?
+    end
+  end
+
+  class ComplexRelationTest < MySQLIntegrationTest
+    setup do
+      @parent = UuidParent.new(id: SecureRandom.uuid.upcase)
+    end
+
+    teardown do
+      UuidParent.delete_all
+      UuidChild.delete_all
+    end
+
+    test "does not dirty data on association reloads" do
+      @parent.uuid_children.build
+      @parent.save!
+      @parent.uuid_children.reload
+
+      refute @parent.uuid_children.first.uuid_parent_id_changed?
+    end
   end
 end