diff --git a/config/initializers/custom_errors.rb b/config/initializers/custom_errors.rb
new file mode 100644
index 0000000000..a7396eb59b
--- /dev/null
+++ b/config/initializers/custom_errors.rb
@@ -0,0 +1,22 @@
+# This patch customises ActiveModel error messages, as previously handled by the custom_error_messages gem
+# See: https://github.com/jeremydurham/custom-err-msg
+
+module ActiveModel
+  class Error
+    def self.full_message(attribute, message, base)
+      return message if attribute == :base
+
+      attr_name = attribute.to_s.tr(".", "_").humanize
+      attr_name = base.class.human_attribute_name(attribute, {
+        default: attr_name,
+        base: base,
+      })
+
+      if message.start_with?("^")
+        I18n.t("errors.format.full_message", default: "%{message}", message: message[1..-1], attribute: attr_name)
+      else
+        I18n.t("errors.format", default: "%{attribute} %{message}", message: message, attribute: attr_name)
+      end
+    end
+  end
+end