diff --git a/lib/bitmask_attributes.rb b/lib/bitmask_attributes.rb
index 9d80f79..01dd34d 100644
--- a/lib/bitmask_attributes.rb
+++ b/lib/bitmask_attributes.rb
@@ -38,7 +38,7 @@ def bitmask(attribute, options={}, &extension)
 
       if default = options[:default]
         after_initialize do
-          send("#{attribute}=", default) unless send("#{attribute}?")
+          send("#{attribute}=", default) unless read_attribute(attribute)
         end
       end
 
@@ -75,6 +75,7 @@ def bitmask(attribute, options={}, &extension)
       end
 
       define_method "#{attribute}=" do |value|
+        value ||= default if default
         if value.is_a?(Fixnum)
           value = self.class.send("#{attribute}_for_bitmask", value)
         end
diff --git a/test/bitmask_attributes_test.rb b/test/bitmask_attributes_test.rb
index dca0564..08232a5 100644
--- a/test/bitmask_attributes_test.rb
+++ b/test/bitmask_attributes_test.rb
@@ -314,6 +314,12 @@ def assert_stored(record, *values)
     assert_equal DefaultValue.new.default_array, [:y, :z]
     assert_equal DefaultValue.new(:default_sym => :x).default_sym, [:x]
     assert_equal DefaultValue.new(:default_array => [:x]).default_array, [:x]
+    assert_equal DefaultValue.new(:default_sym => []).default_sym, []
+
+    default_value = DefaultValue.new(:default_sym => :x)
+
+    default_value.default_sym = nil
+    assert_equal default_value.default_sym, [:y]
   end
 
   context_with_classes 'Campaign with null attributes',CampaignWithNull,CompanyWithNull