diff --git a/includes/functions.php b/includes/functions.php
index b04a5f3..1504bac 100644
--- a/includes/functions.php
+++ b/includes/functions.php
@@ -3423,7 +3423,7 @@ function thold_check_threshold(&$thold_data) {
 		}
 	}
 
-	if (api_plugin_is_enabled('maint') && plugin_maint_check_cacti_host($thold_data['host_id'])) {
+	if (api_plugin_is_enabled('maint') && function_exists('plugin_maint_check_cacti_host') && plugin_maint_check_cacti_host($thold_data['host_id'])) {
 		$maint_dev = true;
 	} else {
 		$maint_dev = false;
diff --git a/includes/polling.php b/includes/polling.php
index 51b6898..202ed2f 100644
--- a/includes/polling.php
+++ b/includes/polling.php
@@ -637,7 +637,7 @@ function thold_update_host_status() {
 				$msg = thold_str_replace('<NOTES>', $host['notes'], $msg);
 				$msg = thold_str_replace("\n", '<br>', $msg);
 
-				if (api_plugin_is_enabled('maint') && plugin_maint_check_cacti_host($host['id'])) {
+				if (api_plugin_is_enabled('maint') && function_exists('plugin_maint_check_cacti_host') && plugin_maint_check_cacti_host($host['id'])) {
 					cacti_log('WARNING: Device[' . $host['id'] . '] Hostname[' . $host['hostname'] . '] is recovering! Only logging, maint device', true, 'THOLD');
 				} else {
 					switch ($host['thold_send_email']) {
@@ -764,7 +764,7 @@ function thold_update_host_status() {
 
 			$alert_email = read_config_option('alert_email');
 
-			if (api_plugin_is_enabled('maint') && plugin_maint_check_cacti_host($host['id'])) {
+			if (api_plugin_is_enabled('maint') && function_exists('plugin_maint_check_cacti_host') && plugin_maint_check_cacti_host($host['id'])) {
 				cacti_log('WARNING: Device[' . $host['id'] . '] Hostname[' . $host['hostname'] . '] is DOWN. Only logging, maint device', true, 'THOLD');
 			} else {
 				if (strtotime($host['status_fail_date']) > 192800 || strtotime($host['status_rec_date']) > 192800) {
diff --git a/tests/Unit/MaintCheckGuardTest.php b/tests/Unit/MaintCheckGuardTest.php
new file mode 100644
index 0000000..22b2531
--- /dev/null
+++ b/tests/Unit/MaintCheckGuardTest.php
@@ -0,0 +1,123 @@
+<?php
+/*
+ +-------------------------------------------------------------------------+
+ | Copyright (C) 2004-2026 The Cacti Group                                 |
+ |                                                                         |
+ | This program is free software; you can redistribute it and/or           |
+ | modify it under the terms of the GNU General Public License             |
+ | as published by the Free Software Foundation; either version 2          |
+ | of the License, or (at your option) any later version.                  |
+ +-------------------------------------------------------------------------+
+ | Cacti: The Complete RRDtool-based Graphing Solution                     |
+ +-------------------------------------------------------------------------+
+ | http://www.cacti.net/                                                   |
+ +-------------------------------------------------------------------------+
+*/
+
+/**
+ * thold_update_host_status() consults the maint plugin for both the
+ * recovering-device and down-device notification loops. The call is now
+ * guarded by function_exists('plugin_maint_check_cacti_host') so a maint
+ * plugin that is enabled but whose functions file could not be included no
+ * longer fatals with an undefined-function error. These tests drive both
+ * maintenance-gated branches so that guard stays in place.
+ */
+final class MaintCheckGuardTest extends TestCase {
+	/**
+	 * @return void
+	 */
+	public static function setUpBeforeClass(): void {
+		self::loadPluginSource('includes/functions.php');
+		self::loadPluginSource('includes/polling.php');
+		self::loadPluginSourceAlways('includes/arrays.php');
+		self::loadPluginConstants();
+	}
+
+	/**
+	 * @return string
+	 */
+	private function maintIncludesRoot() {
+		return dirname(__DIR__) . '/Fixtures/cacti-root-maint-includes';
+	}
+
+	/**
+	 * Run thold_update_host_status() against the newer maint layout. A device
+	 * inside a maintenance window is logged and the loop moves on without the
+	 * downstream notification work, so the call returns on its own. Expected
+	 * engine warnings are suppressed, but no Throwable is swallowed, so an
+	 * unexpected error (e.g. a removed guard fataling on an undefined maint
+	 * function) fails the test.
+	 *
+	 * @return void
+	 */
+	private function runHostStatus() {
+		CactiStubs::willAlwaysReturn('api_plugin_is_enabled', true);
+		CactiStubs::willAlwaysReturn('plugin_maint_check_cacti_host', true);
+		CactiStubs::$configOptions['alert_deadnotify'] = 'on';
+		$GLOBALS['config']['base_path'] = $this->maintIncludesRoot();
+
+		set_error_handler(static fn (): bool => true);
+		ob_start();
+
+		try {
+			thold_update_host_status();
+		} finally {
+			ob_end_clean();
+			restore_error_handler();
+		}
+	}
+
+	/**
+	 * A recovered device inside a maintenance window is logged, not alerted.
+	 *
+	 * @return void
+	 */
+	public function testRecoveringDeviceInMaintenanceIsLoggedNotAlerted(): void {
+		CactiStubs::willReturnFor('db_fetch_assoc', 'plugin_thold_host_failed', [['host_id' => 42]]);
+		CactiStubs::willReturnFor('db_fetch_row_prepared', 'FROM host WHERE id', [
+			'id'               => 42,
+			'hostname'         => 'dev42',
+			'description'      => 'Device 42',
+			'status'           => HOST_UP,
+			'snmp_community'   => '',
+			'snmp_username'    => '',
+			'snmp_version'     => 0,
+			'site_id'          => 0,
+			'location'         => '',
+			'notes'            => '',
+			'status_fail_date' => '0000-00-00 00:00:00',
+			'availability'     => 100,
+			'total_polls'      => 1,
+			'failed_polls'     => 0,
+			'cur_time'         => 0,
+			'avg_time'         => 0,
+			'thold_send_email' => '0',
+		]);
+
+		$this->runHostStatus();
+
+		$this->assertContains(
+			'WARNING: Device[42] Hostname[dev42] is recovering! Only logging, maint device',
+			CactiStubs::$log
+		);
+	}
+
+	/**
+	 * A down device inside a maintenance window is logged, not alerted.
+	 *
+	 * @return void
+	 */
+	public function testDownDeviceInMaintenanceIsLoggedNotAlerted(): void {
+		CactiStubs::willReturnFor('db_fetch_assoc_prepared', 'availability_method', [[
+			'id'       => 77,
+			'hostname' => 'dev77',
+		]]);
+
+		$this->runHostStatus();
+
+		$this->assertContains(
+			'WARNING: Device[77] Hostname[dev77] is DOWN. Only logging, maint device',
+			CactiStubs::$log
+		);
+	}
+}
diff --git a/tests/bootstrap-unit.php b/tests/bootstrap-unit.php
index ae80db4..bfffd08 100644
--- a/tests/bootstrap-unit.php
+++ b/tests/bootstrap-unit.php
@@ -669,6 +669,12 @@ if (!function_exists('number_format_i18n')) {
 	}
 }
 
+if (!function_exists('html_split_string')) {
+	function html_split_string($string, $length = 76, $forgiving = 10) {
+		return $string;
+	}
+}
+
 if (!defined('FILTER_VALIDATE_IS_REGEX')) {
 	define('FILTER_VALIDATE_IS_REGEX', 99999);
 }