diff --git a/packages/svelte/src/compiler/index.js b/packages/svelte/src/compiler/index.js
index 42427dd9c4..756a88a824 100644
--- a/packages/svelte/src/compiler/index.js
+++ b/packages/svelte/src/compiler/index.js
@@ -43,6 +43,11 @@ export function compile(source, options) {
 			instance: parsed.instance && remove_typescript_nodes(parsed.instance),
 			module: parsed.module && remove_typescript_nodes(parsed.module)
 		};
+		if (combined_options.customElementOptions?.extend) {
+			combined_options.customElementOptions.extend = remove_typescript_nodes(
+				combined_options.customElementOptions?.extend
+			);
+		}
 	}
 
 	const analysis = analyze_component(parsed, source, combined_options);
diff --git a/packages/svelte/src/compiler/phases/1-parse/index.js b/packages/svelte/src/compiler/phases/1-parse/index.js
index 5c72d2003f..6cc5b58aa6 100644
--- a/packages/svelte/src/compiler/phases/1-parse/index.js
+++ b/packages/svelte/src/compiler/phases/1-parse/index.js
@@ -143,7 +143,7 @@ export class Parser {
 		if (options_index !== -1) {
 			const options = /** @type {AST.SvelteOptionsRaw} */ (this.root.fragment.nodes[options_index]);
 			this.root.fragment.nodes.splice(options_index, 1);
-			this.root.options = read_options(options, this.ts);
+			this.root.options = read_options(options);
 
 			disallow_children(options);
 
diff --git a/packages/svelte/src/compiler/phases/1-parse/read/options.js b/packages/svelte/src/compiler/phases/1-parse/read/options.js
index 51c682ade7..a36e101468 100644
--- a/packages/svelte/src/compiler/phases/1-parse/read/options.js
+++ b/packages/svelte/src/compiler/phases/1-parse/read/options.js
@@ -2,14 +2,12 @@
 /** @import { AST } from '#compiler' */
 import { NAMESPACE_MATHML, NAMESPACE_SVG } from '../../../../constants.js';
 import * as e from '../../../errors.js';
-import { remove_typescript_nodes } from '../remove_typescript_nodes.js';
 
 /**
  * @param {AST.SvelteOptionsRaw} node
- * @param {boolean} ts
  * @returns {AST.Root['options']}
  */
-export default function read_options(node, ts) {
+export default function read_options(node) {
 	/** @type {AST.SvelteOptions} */
 	const component_options = {
 		start: node.start,
@@ -144,7 +142,7 @@ export default function read_options(node, ts) {
 
 				const extend = properties.find(([name]) => name === 'extend')?.[1];
 				if (extend) {
-					ce.extend = ts ? remove_typescript_nodes(extend) : extend;
+					ce.extend = extend;
 				}
 
 				component_options.customElement = ce;