diff --git a/.changeset/smart-forks-double.md b/.changeset/smart-forks-double.md
new file mode 100644
index 000000000000..e98f3bbab9e3
--- /dev/null
+++ b/.changeset/smart-forks-double.md
@@ -0,0 +1,5 @@
+---
+'@sveltejs/package': patch
+---
+
+fix check for undefined on application/ strip
diff --git a/packages/package/src/utils.js b/packages/package/src/utils.js
index 0b263857b54c..0019706103a7 100644
--- a/packages/package/src/utils.js
+++ b/packages/package/src/utils.js
@@ -52,7 +52,7 @@ export function strip_lang_tags(content) {
 		.replace(
 			/(<!--[^]*?-->)|(<script[^>]*?)\s(?:type|lang)=(["'])(.*?)\3/g,
 			// things like application/ld+json should be kept as-is. Preprocessed languages are "ts" etc
-			(match, s1, s2, _, s4) => (s4.startsWith('application/') ? match : (s1 ?? '') + (s2 ?? ''))
+			(match, s1, s2, _, s4) => (s4?.startsWith('application/') ? match : (s1 ?? '') + (s2 ?? ''))
 		)
 		.replace(/(<!--[^]*?-->)|(<style[^>]*?)\s(?:type|lang)=(["']).*?\3/g, '$1$2');
 }