diff --git a/Gemfile.lock b/Gemfile.lock
index 489ea72c..1a5b55c4 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -526,8 +526,8 @@ GEM
       rubyzip (~> 1.2, >= 1.2.2)
     sexp_processor (4.11.0)
     shellany (0.0.1)
-    shoulda-matchers (3.1.2)
-      activesupport (>= 4.0.0)
+    shoulda-matchers (4.0.1)
+      activesupport (>= 4.2.0)
     simplecov (0.16.1)
       docile (~> 1.1)
       json (>= 1.8, < 3)
diff --git a/app/models/registration.rb b/app/models/registration.rb
index a071af28..84a9aba0 100644
--- a/app/models/registration.rb
+++ b/app/models/registration.rb
@@ -31,7 +31,7 @@ class Registration < ApplicationRecord
   validate :registration_to_events_only_if_present
 
   validates :accepted_code_of_conduct, acceptance: {
-    if: -> { conference.code_of_conduct.present? }
+    if: -> { conference.try(:code_of_conduct).present? }
   }
 
   after_create :set_week, :subscribe_to_conference, :send_registration_mail