diff --git a/.changeset/silly-mirrors-give.md b/.changeset/silly-mirrors-give.md
new file mode 100644
index 0000000000..baa94162f9
--- /dev/null
+++ b/.changeset/silly-mirrors-give.md
@@ -0,0 +1,5 @@
+---
+'@astrojs/webapi': patch
+---
+
+Fix CustomElementRegistry for Node SSR Adapter
diff --git a/packages/webapi/src/lib/CustomElementRegistry.ts b/packages/webapi/src/lib/CustomElementRegistry.ts
index 3429e1e730..21f775d5e5 100644
--- a/packages/webapi/src/lib/CustomElementRegistry.ts
+++ b/packages/webapi/src/lib/CustomElementRegistry.ts
@@ -81,8 +81,9 @@ export const initCustomElementRegistry = (
 	const CustomElementRegistry =
 		target.CustomElementRegistry || globalThis.CustomElementRegistry
 
-	const customElements: CustomElementRegistry = (target.customElements =
-		Object.create(CustomElementRegistry.prototype))
+	const customElements: CustomElementRegistry =
+		target.customElements ||
+		(target.customElements = new CustomElementRegistry())
 
 	_.INTERNALS.set(customElements, {
 		constructorByName: new Map(),