diff --git a/2meet-data-optimizer.php b/2meet-data-optimizer.php
index 3320d51..5fa0c00 100644
--- a/2meet-data-optimizer.php
+++ b/2meet-data-optimizer.php
@@ -88,7 +88,11 @@ if ( version_compare( PHP_VERSION, TMDO_MIN_PHP, '<' ) ) {
 add_action(
 	'admin_notices',
 	static function () {
-		if ( defined( 'WPDO_VERSION' ) && WPDO_VERSION !== TMDO_VERSION ) {
+		// Deliberately not a WPDO_VERSION comparison: this plugin defines that
+		// constant itself (includes/class-tmdo-back-compat.php), so the two
+		// would always match and the notice could never fire.
+		$tmdo_legacy = 'wp-data-optimizer/wp-data-optimizer.php';
+		if ( in_array( $tmdo_legacy, (array) get_option( 'active_plugins', array() ), true ) ) {
 			echo '<div class="notice notice-error"><p>';
 			esc_html_e( '⚠ 偵測到舊版 wp-data-optimizer 已啟用。請停用舊外掛以避免 hook 雙觸發。', '2meet-data-optimizer' );
 			echo '</p></div>';