diff --git a/app/calculation/exercise_resource_usage.rb b/app/calculation/exercise_resource_usage.rb
index 1e97896d..980c5251 100644
--- a/app/calculation/exercise_resource_usage.rb
+++ b/app/calculation/exercise_resource_usage.rb
@@ -15,6 +15,6 @@ def result
         results[:cpu] += (vm.cpu || vm.operating_system&.applied_cpu).to_i * instance_count
         results[:primary_disk_size] += (vm.primary_disk_size || vm.operating_system&.applied_primary_disk_size).to_i * instance_count
       end
-      OpenStruct.new(results)
+      Struct.new(*results.keys).new(**results)
     end
 end
diff --git a/app/calculation/hostname_generator.rb b/app/calculation/hostname_generator.rb
index 3bddf635..4288ec4b 100644
--- a/app/calculation/hostname_generator.rb
+++ b/app/calculation/hostname_generator.rb
@@ -13,11 +13,11 @@ def result
       hostname = "#{subject.hostname}#{sequences.join('_')}"
       domain = nic&.network&.full_domain.to_s.gsub(/#+/, '{{ team_nr_str }}')
 
-      OpenStruct.new({
+      Struct.new(:hostname, :domain, :fqdn).new(
         hostname:,
         domain:,
         fqdn: "#{hostname}.#{domain}"
-      })
+      )
     end
 
     def virtual_machine
diff --git a/app/calculation/liquid_range_substitution.rb b/app/calculation/liquid_range_substitution.rb
index 09d26199..3ed30466 100644
--- a/app/calculation/liquid_range_substitution.rb
+++ b/app/calculation/liquid_range_substitution.rb
@@ -25,7 +25,7 @@ def numbering_actor
                             vm_numbering_source(subject)
                           else
                             subject.actor
-                          end
+      end
     end
 
     def vm_numbering_source(vm)
diff --git a/app/helpers/network_helper.rb b/app/helpers/network_helper.rb
index b3f9a5dc..eff8de3f 100644
--- a/app/helpers/network_helper.rb
+++ b/app/helpers/network_helper.rb
@@ -9,7 +9,7 @@ def sorted_used_addresses(network)
       [
         vm,
         addresses
-          .sort_by {|a| a.offset.to_s }
+          .sort_by { |a| a.offset.to_s }
           .group_by(&:ip_family)
           .reverse_merge({ ipv4: [], ipv6: [] })
       ]
diff --git a/app/views/exercises/show.html.haml b/app/views/exercises/show.html.haml
index acb300a3..63fcc036 100644
--- a/app/views/exercises/show.html.haml
+++ b/app/views/exercises/show.html.haml
@@ -77,7 +77,6 @@
       %i.fas.fa-plus.self-center
       Add actor
 
-
 #actors.grid.gap-4.grid-cols-1.lg:grid-cols-2
   - @actors.each do |actor, tree|
     = render 'actor', actor:, tree:
diff --git a/spec/models/service_subject_spec.rb b/spec/models/service_subject_spec.rb
index 08bc8a56..96e9025e 100644
--- a/spec/models/service_subject_spec.rb
+++ b/spec/models/service_subject_spec.rb
@@ -3,7 +3,6 @@
 require 'rails_helper'
 
 RSpec.describe ServiceSubject do
-
   context 'spec cache' do
     subject { create(:service_subject, service:) }
     let(:service) { create(:service) }