diff --git a/src/blot/abstract/parent.ts b/src/blot/abstract/parent.ts
index 2b1c5fd..c8ea687 100644
--- a/src/blot/abstract/parent.ts
+++ b/src/blot/abstract/parent.ts
@@ -351,7 +351,7 @@ class ParentBlot extends ShadowBlot implements Parent {
         node.parentNode != null &&
         // @ts-expect-error Fix me later
         node.tagName !== 'IFRAME' &&
-        document.body.compareDocumentPosition(node) &
+        (node.ownerDocument ?? document).body.compareDocumentPosition(node) &
           Node.DOCUMENT_POSITION_CONTAINED_BY
       ) {
         return;
diff --git a/src/registry.ts b/src/registry.ts
index 45cc4ec..6092a30 100644
--- a/src/registry.ts
+++ b/src/registry.ts
@@ -83,7 +83,11 @@ export default class Registry implements RegistryInterface {
       } else if (query & Scope.LEVEL & Scope.INLINE) {
         match = this.types.inline;
       }
-    } else if (query instanceof Element) {
+    } else if (
+      query instanceof HTMLElement ||
+      query instanceof
+        (query.ownerDocument?.defaultView?.HTMLElement ?? HTMLElement)
+    ) {
       const names = (query.getAttribute('class') || '').split(/\s+/);
       names.some((name) => {
         match = this.classes[name];