diff --git a/config/initializers/0_fix_psych.rb b/config/initializers/0_fix_psych.rb
new file mode 100644
index 0000000000..f3b1a81c9a
--- /dev/null
+++ b/config/initializers/0_fix_psych.rb
@@ -0,0 +1,9 @@
+# Ruby 3.1 includes a breaking update to Psych 4.
+# Undo the breakage, as Mastodon doesn't load untrusted YAML files.
+# https://stackoverflow.com/a/71192990
+
+module YAML
+  class << self
+    alias_method :load, :unsafe_load if YAML.respond_to? :unsafe_load
+  end
+end