when you're editing a existing timelog entry and have the rights to adjust the user ( or log on behalf of another user ), the current value will not be selected in the drop down due to this line:

https://www.redmine.org/projects/redmine/repository/revisions/19326/entry/branches/4.1-stable/app/helpers/application_helper.rb#L578

the fix is quite simple, just drop the @.to_s@

      selected_attribute = ' selected="selected"' if option_value_selected?(element, selected) || element.id == selected

and its working.

diff --git a/app/helpers/application_helper.rb b/app/helpers/application_helper.rb
index b40f42ecc..e13825082 100644
--- a/app/helpers/application_helper.rb
+++ b/app/helpers/application_helper.rb
@@ -575,7 +575,7 @@ module ApplicationHelper
     end
     groups = +''
     collection.sort.each do |element|
-      selected_attribute = ' selected="selected"' if option_value_selected?(element, selected) || element.id == selected
+      selected_attribute = ' selected="selected"' if option_value_selected?(element, selected) || element.id.to_s == selected
       (element.is_a?(Group) ? groups : s) << %(#{h element.name})
     end
     unless groups.empty?