diff --git a/.changeset/new-trainers-peel.md b/.changeset/new-trainers-peel.md
new file mode 100644
index 000000000..20eec3abe
--- /dev/null
+++ b/.changeset/new-trainers-peel.md
@@ -0,0 +1,5 @@
+---
+'slate-react': patch
+---
+
+Fix crash when unmounting an editor rendered within a React portal. The issue was arising at unmount time, because `getRootNode` returned the dettached portal node and it is not an instance of `Document` or `ShadowRoot`. As a fix, `getDocumentOrShadowRoot` has been refactored to return a root node instead of throwing. In sum, this patch fixes a regression bug introduced by https://github.com/ianstormtaylor/slate/pull/3749/
diff --git a/packages/slate-react/src/plugin/react-editor.ts b/packages/slate-react/src/plugin/react-editor.ts
index fe271c90b..b4b3fd383 100644
--- a/packages/slate-react/src/plugin/react-editor.ts
+++ b/packages/slate-react/src/plugin/react-editor.ts
@@ -106,23 +106,14 @@ export const ReactEditor = {
     const el = ReactEditor.toDOMNode(editor, editor)
     const root = el.getRootNode()
 
-    // The below exception will always be thrown for iframes because the document inside an iframe
-    // does not inherit it's prototype from the parent document, therefore we return early
-    if (el.ownerDocument !== document) return el.ownerDocument
+    if (
+      (root instanceof Document || root instanceof ShadowRoot) &&
+      root.getSelection != null
+    ) {
+      return root
+    }
 
-    if (!(root instanceof Document || root instanceof ShadowRoot))
-      throw new Error(
-        `Unable to find DocumentOrShadowRoot for editor element: ${el}`
-      )
-
-    // COMPAT: Only Chrome implements the DocumentOrShadowRoot mixin for
-    // ShadowRoot; other browsers still implement it on the Document
-    // interface. (2020/08/08)
-    // https://developer.mozilla.org/en-US/docs/Web/API/ShadowRoot#Properties
-    if (root.getSelection === undefined && el.ownerDocument !== null)
-      return el.ownerDocument
-
-    return root
+    return el.ownerDocument
   },
 
   /**