--- a/mod_protect_last_admin/mod_protect_last_admin.lua	Thu Sep 25 18:21:27 2025 +0100
+++ b/mod_protect_last_admin/mod_protect_last_admin.lua	Mon Sep 29 21:28:18 2025 +0100
@@ -6,6 +6,19 @@
 
 local protected_roles = module:get_option_set("protect_last_admin_roles", { "prosody:admin", "prosody:operator" });
 
+local errors = require "prosody.util.error".init(module.name, {
+	["cannot-remove-only-admin"] = {
+		code = 400;
+		type = "cancel";
+		condition = "policy-violation";
+		text  = "Cannot remove the only administrator";
+		extra = {
+			namespace = "https://prosody.im/protocol/errors";
+			condition = "cannot-remove-only-admin";
+		};
+	};
+});
+
 local function other_protected_users(username, host)
 	local protected_users = set.new();
 	for protected_role in protected_roles do
@@ -39,7 +52,7 @@
 	end
 
 	if not other_protected_users(username, host) then
-		event.reason = "Cannot remove the only administrator";
+		event.reason = errors.new("cannot-remove-only-admin");
 		return false;
 	end
 	module:log("debug", "Permitting event, no reason not to!");