diff --git a/app/models/user_preference.rb b/app/models/user_preference.rb
index da99061a1..3c46712f9 100644
--- a/app/models/user_preference.rb
+++ b/app/models/user_preference.rb
@@ -44,7 +44,7 @@ class UserPreference < ActiveRecord::Base
     if attribute_present? attr_name
       super
     else
-      h = read_attribute(:others).dup || {}
+      h = (read_attribute(:others) || {}).dup
       h.update(attr_name => value)
       write_attribute(:others, h)
       value
diff --git a/test/unit/user_preference_test.rb b/test/unit/user_preference_test.rb
index 61dea0f59..9f49458eb 100644
--- a/test/unit/user_preference_test.rb
+++ b/test/unit/user_preference_test.rb
@@ -54,4 +54,19 @@ class UserPreferenceTest < ActiveSupport::TestCase
     assert up.save
     assert_kind_of Hash, up.others
   end
+
+  def test_reading_value_from_nil_others_hash
+    up = UserPreference.new(:user => User.new)
+    up.others = nil
+    assert_nil up.others
+    assert_nil up[:foo]
+  end
+
+  def test_writing_value_to_nil_others_hash
+    up = UserPreference.new(:user => User.new)
+    up.others = nil
+    assert_nil up.others
+    up[:foo] = 'bar'
+    assert_equal 'bar', up[:foo]
+  end
 end