diff --git a/app/models/time_entry.rb b/app/models/time_entry.rb
index 91996ba..73f39f9 100644
--- a/app/models/time_entry.rb
+++ b/app/models/time_entry.rb
@@ -44,6 +44,7 @@ class TimeEntry < ActiveRecord::Base
       if default_activity = TimeEntryActivity.default
         self.activity_id = default_activity.id
       end
+      self.hours = nil if hours == 0
     end
   end
   
diff --git a/test/unit/time_entry_test.rb b/test/unit/time_entry_test.rb
index 7ac1c02..3c13551 100644
--- a/test/unit/time_entry_test.rb
+++ b/test/unit/time_entry_test.rb
@@ -44,4 +44,8 @@ class TimeEntryTest < ActiveSupport::TestCase
       assert_equal v, t.hours, "Converting #{k} failed:"
     end
   end
+  
+  def test_hours_should_default_to_nil
+    assert_nil TimeEntry.new.hours
+  end
 end