Attributes should not exist in the db if value was nil

lib/mongoid/attributes.rb

@@ -43,7 +43,7 @@ def process(attrs = {})
           if Mongoid.allow_dynamic_fields && !respond_to?("#{key}=")
             @attributes[key.to_s] = value
           else
-            send("#{key}=", value)
+            send("#{key}=", value) if value
           end
         end
       end

spec/integration/mongoid/attributes_spec.rb

@@ -0,0 +1,22 @@
+require "spec_helper"
+
+describe Mongoid::Attributes do
+
+  context "when persisting nil attributes" do
+
+    before do
+      @person = Person.create(:score => nil, :ssn => "555-66-7777")
+    end
+
+    after do
+      Person.delete_all
+    end
+
+    it "the field should not exist" do
+      from_db = Person.find(@person.id)
+      from_db.attributes.has_key?(:score).should be_false
+    end
+
+  end
+
+end