diff -r c3feb0e8d7c4 app/models/time_entry.rb
--- a/app/models/time_entry.rb	Fri Dec 25 16:52:01 2020 +0330
+++ b/app/models/time_entry.rb	Mon Mar 08 18:45:41 2021 +0330
@@ -114,7 +114,16 @@
           end
           @invalid_issue_id = nil
         else
-          @invalid_issue_id = issue_id
+          if user.allowed_to?(:log_time, issue.project) && issue.assigned_to_id_changed?
+            tmp_previous_assignee = issue.assigned_to
+            issue.assigned_to = issue.previous_assignee
+            if !issue.visible?(user)
+              @invalid_issue_id = issue_id
+            end
+            issue.assigned_to = tmp_previous_assignee
+          else
+            @invalid_issue_id = issue_id
+          end
         end
       end
       if user_id_changed? && user_id != author_id && !user.allowed_to?(:log_time_for_other_users, project)