Index: field_format.rb
===================================================================
diff --git a/trunk/lib/redmine/field_format.rb b/trunk/lib/redmine/field_format.rb
--- a/trunk/lib/redmine/field_format.rb	(revision 20121)
+++ b/trunk/lib/redmine/field_format.rb	(working copy)
@@ -611,7 +611,7 @@
         blank_option = ''.html_safe
         unless custom_value.custom_field.multiple?
           if custom_value.custom_field.is_required?
-            unless custom_value.custom_field.default_value.present?
+            unless custom_value.custom_field.default_value.present? && custom_value.customized.new_record?
               blank_option = view.content_tag('option', "--- #{l(:actionview_instancetag_blank_option)} ---", :value => '')
             end
           else