diff --git a/app/models/address.rb b/app/models/address.rb
index 2dd61f739..89a05a730 100644
--- a/app/models/address.rb
+++ b/app/models/address.rb
@@ -1,3 +1,3 @@
 class Address < ApplicationRecord
-  belongs_to :sponsor
+  belongs_to :sponsor, optional: true
 end
diff --git a/app/models/attendance_warning.rb b/app/models/attendance_warning.rb
index 30f395524..b7e722461 100644
--- a/app/models/attendance_warning.rb
+++ b/app/models/attendance_warning.rb
@@ -1,6 +1,6 @@
 class AttendanceWarning < ApplicationRecord
   belongs_to :member
-  belongs_to :issued_by, class_name: 'Member', foreign_key: 'sent_by_id', inverse_of: false
+  belongs_to :issued_by, class_name: 'Member', foreign_key: 'sent_by_id', inverse_of: false, optional: true
 
   scope :last_six_months, -> { where(created_at: 6.months.ago...Time.zone.now) }
 
diff --git a/app/models/auth_service.rb b/app/models/auth_service.rb
index f34e9e5ee..4618b0617 100644
--- a/app/models/auth_service.rb
+++ b/app/models/auth_service.rb
@@ -1,4 +1,4 @@
 class AuthService < ApplicationRecord
-  belongs_to :member
+  belongs_to :member, optional: true
   validates :uid, uniqueness: { constraint: :provider }
 end
diff --git a/app/models/ban.rb b/app/models/ban.rb
index 147b039a1..7b4aee467 100644
--- a/app/models/ban.rb
+++ b/app/models/ban.rb
@@ -1,5 +1,5 @@
 class Ban < ApplicationRecord
-  belongs_to :member
+  belongs_to :member, optional: true
   belongs_to :added_by, class_name: 'Member'
 
   validates :expires_at, :reason, :note, :added_by, presence: true
diff --git a/app/models/contact.rb b/app/models/contact.rb
index 97c44b4cf..e9e8b7279 100644
--- a/app/models/contact.rb
+++ b/app/models/contact.rb
@@ -1,6 +1,6 @@
 require 'services/mailing_list'
 class Contact < ApplicationRecord
-  belongs_to :sponsor
+  belongs_to :sponsor, optional: true
 
   validates :name, :surname, :email, presence: true
 
diff --git a/app/models/event.rb b/app/models/event.rb
index 0bcae8ead..2dd5a784a 100644
--- a/app/models/event.rb
+++ b/app/models/event.rb
@@ -8,7 +8,7 @@ class Event < ApplicationRecord
 
   resourcify :permissions, role_cname: 'Permission', role_table_name: :permission
 
-  belongs_to :venue, class_name: 'Sponsor'
+  belongs_to :venue, class_name: 'Sponsor', optional: true
   has_many :sponsorships
   has_many :sponsors, -> { where('sponsorships.level' => nil) }, through: :sponsorships, source: :sponsor
   has_many :bronze_sponsors, -> { where('sponsorships.level' => 'bronze') }, through: :sponsorships, source: :sponsor
diff --git a/app/models/feedback.rb b/app/models/feedback.rb
index 2da9f8725..d2cd52693 100644
--- a/app/models/feedback.rb
+++ b/app/models/feedback.rb
@@ -1,7 +1,7 @@
 class Feedback < ApplicationRecord
   belongs_to :tutorial
   belongs_to :coach, class_name: 'Member'
-  belongs_to :workshop
+  belongs_to :workshop, optional: true
   has_one :chapter, through: :workshop
 
   validates :rating, inclusion: { in: 1..5, message: "can't be blank" }
diff --git a/app/models/feedback_request.rb b/app/models/feedback_request.rb
index 392f5f0c3..d269bd831 100644
--- a/app/models/feedback_request.rb
+++ b/app/models/feedback_request.rb
@@ -1,6 +1,6 @@
 class FeedbackRequest < ApplicationRecord
   belongs_to :member
-  belongs_to :workshop
+  belongs_to :workshop, optional: true
 
   validates :member_id, presence: true, uniqueness: { scope: [:workshop] }
   validates :workshop, presence: true
diff --git a/app/models/invitation.rb b/app/models/invitation.rb
index bbd43aca9..46d554406 100644
--- a/app/models/invitation.rb
+++ b/app/models/invitation.rb
@@ -3,7 +3,7 @@ class Invitation < ApplicationRecord
 
   belongs_to :event
   belongs_to :member
-  belongs_to :verified_by, class_name: 'Member'
+  belongs_to :verified_by, class_name: 'Member', optional: true
 
   validates :event, :member, presence: true
   validates :member_id, uniqueness: { scope: %i[event_id role] }
diff --git a/app/models/meeting_talk.rb b/app/models/meeting_talk.rb
index 4ad57e2b9..7a75b1441 100644
--- a/app/models/meeting_talk.rb
+++ b/app/models/meeting_talk.rb
@@ -1,6 +1,6 @@
 class MeetingTalk < ApplicationRecord
-  belongs_to :speaker, class_name: 'Member'
-  belongs_to :meeting
+  belongs_to :speaker, class_name: 'Member', optional: true
+  belongs_to :meeting, optional: true
 
   validates :title, :abstract, :speaker, :meeting, presence: true
 
diff --git a/app/models/member_note.rb b/app/models/member_note.rb
index d4c9d29fc..04d64e60a 100644
--- a/app/models/member_note.rb
+++ b/app/models/member_note.rb
@@ -1,6 +1,6 @@
 class MemberNote < ApplicationRecord
-  belongs_to :member
-  belongs_to :author, class_name: 'Member'
+  belongs_to :member, optional: true
+  belongs_to :author, class_name: 'Member', optional: true
 
   validates :member, :author, :note, presence: true
 end
diff --git a/app/models/permission.rb b/app/models/permission.rb
index 1f6a7f8de..1c2957190 100644
--- a/app/models/permission.rb
+++ b/app/models/permission.rb
@@ -1,6 +1,6 @@
 class Permission < ApplicationRecord
   has_and_belongs_to_many :members, join_table: :members_permissions
-  belongs_to :resource, polymorphic: true
+  belongs_to :resource, polymorphic: true, optional: true
 
   scopify
 end
diff --git a/app/models/tutorial.rb b/app/models/tutorial.rb
index e3fb6e5db..3d081d271 100644
--- a/app/models/tutorial.rb
+++ b/app/models/tutorial.rb
@@ -1,5 +1,5 @@
 class Tutorial < ApplicationRecord
-  belongs_to :workshop
+  belongs_to :workshop, optional:  true
 
   validates :title, presence: true
   default_scope -> { order(:created_at) }
diff --git a/app/models/workshop_invitation.rb b/app/models/workshop_invitation.rb
index ecd4b560e..d61b48109 100644
--- a/app/models/workshop_invitation.rb
+++ b/app/models/workshop_invitation.rb
@@ -3,7 +3,7 @@ class WorkshopInvitation < ApplicationRecord
 
   belongs_to :workshop
   belongs_to :member
-  belongs_to :overrider, foreign_key: :last_overridden_by_id, class_name: 'Member', inverse_of: false
+  belongs_to :overrider, foreign_key: :last_overridden_by_id, class_name: 'Member', inverse_of: false, optional: true
   has_one :waiting_list, foreign_key: :invitation_id
 
   validates :workshop, :member, presence: true
diff --git a/config/application.rb b/config/application.rb
index b3094236d..ab54bece5 100644
--- a/config/application.rb
+++ b/config/application.rb
@@ -57,9 +57,7 @@ class Application < Rails::Application
     # More info at https://skylight.io/support/environments
     config.skylight.environments << 'development'
 
-    # TODO: sort this out properly at 
-    # See https://guides.rubyonrails.org/upgrading_ruby_on_rails.html#active-record-belongs-to-required-by-default-option
-    config.active_record.belongs_to_required_by_default = false
+    config.active_record.belongs_to_required_by_default = true
   end
 end