diff --git a/app/models/custom_field.rb b/app/models/custom_field.rb
index 8d7927ab1..2762f0ee2 100644
--- a/app/models/custom_field.rb
+++ b/app/models/custom_field.rb
@@ -51,7 +51,7 @@ class CustomField < ActiveRecord::Base
   def possible_values_options(obj=nil)
     case field_format
     when 'user', 'version'
-      if obj.respond_to?(:project)
+      if obj.respond_to?(:project) && obj.project
         case field_format
         when 'user'
           obj.project.users.sort.collect {|u| [u.to_s, u.id.to_s]}
diff --git a/test/unit/custom_field_user_format_test.rb b/test/unit/custom_field_user_format_test.rb
index 085e4c73a..5cc4ea5c1 100644
--- a/test/unit/custom_field_user_format_test.rb
+++ b/test/unit/custom_field_user_format_test.rb
@@ -36,6 +36,11 @@ class CustomFieldUserFormatTest < ActiveSupport::TestCase
     assert_equal project.users.sort.collect(&:id).map(&:to_s), possible_values
   end
   
+  def test_possible_values_with_nil_project_resource
+    project = Project.find(1)
+    assert_equal [], @field.possible_values(Issue.new)
+  end
+  
   def test_possible_values_options_with_no_arguments
     assert_equal [], @field.possible_values_options
     assert_equal [], @field.possible_values_options(nil)