diff --git a/src/core/context/node.js b/src/core/context/node.js
index cf6d5a6a80a0..7ac6d0624a24 100644
--- a/src/core/context/node.js
+++ b/src/core/context/node.js
@@ -15,6 +15,7 @@ import {Values} from './values';
 const NODE_PROP = '__AMP_NODE';
 const ASSIGNED_SLOT_PROP = '__AMP_ASSIGNED_SLOT';
 const AMP_PREFIX = 'AMP-';
+const AMPDOC_PROP = '__AMPDOC';
 
 // Relevant node types.
 // See https://developer.mozilla.org/en-US/docs/Web/API/Node/nodeType.
@@ -192,14 +193,14 @@ export class ContextNode {
     this.name = name;
 
     /**
-     * Whether this node is a root. The Document DOM nodes are automatically
+     * Whether this node is a root. The Document DOM nodes and ampdoc roots are automatically
      * considered as roots. But other nodes can become roots as well
      * (e.g. shadow roots) via `setIsRoot()` API.
      *
      * @package
      * @type {boolean}
      */
-    this.isRoot = node.nodeType == DOCUMENT_NODE;
+    this.isRoot = node.nodeType == DOCUMENT_NODE || !!node[AMPDOC_PROP];
 
     /**
      * The root context node. Always available for a DOM node connected to a
diff --git a/src/core/context/types.d.ts b/src/core/context/types.d.ts
index 931c829535cc..3284e911432d 100644
--- a/src/core/context/types.d.ts
+++ b/src/core/context/types.d.ts
@@ -1,4 +1,5 @@
 import {ContextNode} from './node';
+
 export interface IContextProp<T, DEP> {
   /**
    * A globally unique key. Extensions must use a fully qualified name such
@@ -92,5 +93,7 @@ declare global {
 
     // Used to map a Node to its assigned slot.
     __AMP_ASSIGNED_SLOT?: Node;
+
+    __AMPDOC?: import('../../service/ampdoc-impl').AmpDoc;
   }
 }
diff --git a/test/unit/core/context/test-node-discover.js b/test/unit/core/context/test-node-discover.js
index 71147679e045..77f48072f461 100644
--- a/test/unit/core/context/test-node-discover.js
+++ b/test/unit/core/context/test-node-discover.js
@@ -161,6 +161,23 @@ describes.realWin('ContextNode', {}, (env) => {
       });
     });
 
+    it('should create a ampdoc holder shadow root', () => {
+      const frag = doc.createDocumentFragment();
+
+      frag.__AMPDOC = {};
+
+      const cn = ContextNode.get(frag);
+      expect(cn.node).to.equal(frag);
+      // Parent always starts as null.
+      expectContext(cn, {
+        parent: null,
+        isRoot: true,
+        root: frag,
+        children: [],
+        discoverable: false,
+      });
+    });
+
     it('should create a document node', () => {
       const cn = ContextNode.get(doc);
       expect(cn.node).to.equal(doc);