diff --git a/config/initializers/devise.rb b/config/initializers/devise.rb
index cd9bacf68033e609abf0e662b9958b8b00555499..3e4c9a79d7afad792bda0ca917d6a14d967c0de1 100644
--- a/config/initializers/devise.rb
+++ b/config/initializers/devise.rb
@@ -10,6 +10,7 @@ Warden::Manager.after_set_user except: :fetch do |user, warden|
     expires: 1.year.from_now,
     httponly: true,
     secure: (Rails.env.production? || ENV['LOCAL_HTTPS'] == 'true'),
+    same_site: :lax,
   }
 end
 
@@ -20,6 +21,7 @@ Warden::Manager.after_fetch do |user, warden|
       expires: 1.year.from_now,
       httponly: true,
       secure: (Rails.env.production? || ENV['LOCAL_HTTPS'] == 'true'),
+      same_site: :lax,
     }
   else
     warden.logout
diff --git a/config/initializers/session_store.rb b/config/initializers/session_store.rb
index 3dc0edd6fd262f70a6c496c922beb97bd096003c..c0757b6b5730915f1178ca3e7ef512b1fb1bc9b8 100644
--- a/config/initializers/session_store.rb
+++ b/config/initializers/session_store.rb
@@ -1,3 +1,3 @@
 # Be sure to restart your server when you modify this file.
 
-Rails.application.config.session_store :cookie_store, key: '_mastodon_session', secure: (Rails.env.production? || ENV['LOCAL_HTTPS'] == 'true')
+Rails.application.config.session_store :cookie_store, key: '_mastodon_session', secure: (Rails.env.production? || ENV['LOCAL_HTTPS'] == 'true'), same_site: :lax
diff --git a/spec/rails_helper.rb b/spec/rails_helper.rb
index c575128e408bc22bde80194cf97a5a5cf67e358d..79e80220c36d42d73dfce79429bbc89d4bfdc71b 100644
--- a/spec/rails_helper.rb
+++ b/spec/rails_helper.rb
@@ -29,6 +29,7 @@ Devise::Test::ControllerHelpers.module_eval do
       value: resource.activate_session(warden.request),
       expires: 1.year.from_now,
       httponly: true,
+      same_site: :lax,
     }
   end
 end