diff --git a/app/views/main/_submission_short.html.haml b/app/views/main/_submission_short.html.haml
--- a/app/views/main/_submission_short.html.haml
+++ b/app/views/main/_submission_short.html.haml
@@ -1,8 +1,8 @@
 
-- if submission==nil
+- if submission.nil?
   = "-"
 - else
-  - if submission.graded_at==nil
+  - if submission.graded_at.nil?
     =t 'main.submitted_at'
     = format_short_time(submission.submitted_at.localtime)
   - else