diff --git a/package.json b/package.json
index dfc756d..a92ecf8 100644
--- a/package.json
+++ b/package.json
@@ -5,7 +5,7 @@
   "main": "index.js",
   "type": "module",
   "scripts": {
-    "build": "deno build.ts --tagName 1.71.1b9 > ubo.js",
+    "build": "deno build.ts --tagName 1.71.1rc0 > ubo.js",
     "test": "node --test"
   },
   "author": {
diff --git a/ubo.js b/ubo.js
index 4be8f44..3ebe736 100644
--- a/ubo.js
+++ b/ubo.js
@@ -119,10 +119,9 @@ function setAttrFn(
     const start = ( ) => {
         if ( applySetAttr() === false ) { return; }
         observer = new MutationObserver(onDomChanged);
-        observer.observe(document.body, {
-            subtree: true,
-            childList: true,
-        });
+        const root = document.documentElement;
+        if ( root instanceof self.Node === false ) { return; }
+        observer.observe(root, { subtree: true, childList: true });
     };
     runAt(( ) => { start(); }, options.runAt || 'idle');
 }
@@ -425,10 +424,9 @@ function setAttrFn(
     const start = ( ) => {
         if ( applySetAttr() === false ) { return; }
         observer = new MutationObserver(onDomChanged);
-        observer.observe(document.body, {
-            subtree: true,
-            childList: true,
-        });
+        const root = document.documentElement;
+        if ( root instanceof self.Node === false ) { return; }
+        observer.observe(root, { subtree: true, childList: true });
     };
     runAt(( ) => { start(); }, options.runAt || 'idle');
 }