diff --git a/packages/core-js/internals/microtask.js b/packages/core-js/internals/microtask.js
index 6df180c61def..36804bed9771 100644
--- a/packages/core-js/internals/microtask.js
+++ b/packages/core-js/internals/microtask.js
@@ -39,7 +39,7 @@ if (!queueMicrotask) {
       process.nextTick(flush);
     };
   // browsers with MutationObserver, except iOS - https://github.com/zloirock/core-js/issues/339
-  } else if (MutationObserver && !IS_IOS) {
+  } else if (MutationObserver && !IS_IOS && document) {
     toggle = true;
     node = document.createTextNode('');
     new MutationObserver(flush).observe(node, { characterData: true });