diff --git a/mu-plugins/_robots-gptbot.php b/mu-plugins/_robots-gptbot.php
new file mode 100644
index 0000000..69040b3
--- /dev/null
+++ b/mu-plugins/_robots-gptbot.php
@@ -0,0 +1,22 @@
+<?php
+
+/*
+ * Plugin Name: Disallow GPTBot
+ * Plugin URI: https://platform.openai.com/docs/gptbot
+ */
+
+add_filter(
+    'robots_txt',
+    static function ($output, $is_public) {
+        $lines = [
+            'User-agent: GPTBot',
+            'Disallow: /',
+        ];
+        if (!$is_public) {
+            return $output;
+        }
+        return implode("\n", $lines) . "\n\n" . $output;
+    },
+    -1,
+    2
+);
diff --git a/mu-plugins/_robots-oszkbot.php b/mu-plugins/_robots-oszkbot.php
index 24e9edf..3c2b04a 100644
--- a/mu-plugins/_robots-oszkbot.php
+++ b/mu-plugins/_robots-oszkbot.php
@@ -7,15 +7,15 @@
 
 add_filter(
     'robots_txt',
-    static function ($output, $isPublic) {
+    static function ($output, $is_public) {
         $lines = [
             'User-agent: OSZKbot',
             'Disallow: /',
         ];
-        if ($isPublic) {
-            return implode("\n", $lines) . "\n\n" . $output;
+        if (!$is_public) {
+            return $output;
         }
-        return $output;
+        return implode("\n", $lines) . "\n\n" . $output;
     },
     -1,
     2