diff --git a/src/file.ts b/src/file.ts
index 0eaa81f..cfcc418 100644
--- a/src/file.ts
+++ b/src/file.ts
@@ -14,16 +14,6 @@ const TYPE_REG = /id=(\d+)&type=(img|mp3|midi)/
 const magicHookConstr = (() => {
   const l = {}
 
-  // get rid of `Disable Tampermonkey`
-  const observer = new MutationObserver((mutations) => {
-    mutations.forEach(x => [...x.addedNodes].forEach(e => {
-      if (!document.querySelector('.js-page')) {
-        (e as HTMLElement).replaceWith(...x.removedNodes)
-      }
-    }))
-  })
-  observer.observe(document, { childList: true, subtree: true })
-
   try {
     const p = Object.getPrototypeOf(document.body)
     Object.setPrototypeOf(document.body, null)
diff --git a/src/intro.js b/src/intro.js
index ce89c69..3e42822 100644
--- a/src/intro.js
+++ b/src/intro.js
@@ -18,6 +18,16 @@ if (_GM && _GM.registerMenuCommand && _GM.openInTab) {
   )
 }
 
+// get rid of `Disable Tampermonkey`
+const observer = new MutationObserver((mutations) => {
+  mutations.forEach(x => [...x.addedNodes].forEach(e => {
+    if (!document.querySelector('.js-page')) {
+      e.replaceWith(...x.removedNodes)
+    }
+  }))
+})
+observer.observe(document, { childList: true, subtree: true })
+
 // script loader
 new Promise(resolve => {
   const id = '' + Math.random();