diff --git a/app/models/submission.rb b/app/models/submission.rb
index cac3b566..df10d8e4 100644
--- a/app/models/submission.rb
+++ b/app/models/submission.rb
@@ -57,7 +57,7 @@ class Submission < ApplicationRecord
 
   def collect_files
     @collect_files ||= begin
-      ancestors = build_files_hash(exercise.files.includes(:file_type), :id)
+      ancestors = build_files_hash(exercise&.files&.includes(:file_type), :id)
       descendants = build_files_hash(files.includes(:file_type), :file_id)
       ancestors.merge(descendants).values
     end
@@ -209,7 +209,7 @@ class Submission < ApplicationRecord
   private
 
   def build_files_hash(files, attribute)
-    files.map(&attribute.to_proc).zip(files).to_h
+    files&.map(&attribute.to_proc)&.zip(files)&.to_h || {}
   end
 
   def prepared_runner
diff --git a/app/views/submissions/show.html.slim b/app/views/submissions/show.html.slim
index 7109046a..62f58ee7 100644
--- a/app/views/submissions/show.html.slim
+++ b/app/views/submissions/show.html.slim
@@ -7,7 +7,7 @@
 
 h1 = @submission
 
-= row(label: 'submission.exercise', value: link_to_if(policy(@submission.exercise).show?, @submission.exercise, @submission.exercise))
+= row(label: 'submission.exercise', value: link_to_if(@submission.exercise && policy(@submission.exercise).show?, @submission.exercise, @submission.exercise))
 = row(label: 'submission.contributor', value: link_to_if(policy(@submission.contributor).show?, @submission.contributor, @submission.contributor))
 = row(label: 'submission.study_group', value: link_to_if(@submission.study_group.present? && policy(@submission.study_group).show?, @submission.study_group, @submission.study_group))
 = row(label: 'submission.cause', value: t("submissions.causes.#{@submission.cause}"))