diff --git a/.changeset/smart-ears-invent.md b/.changeset/smart-ears-invent.md
new file mode 100644
index 000000000..134618c0d
--- /dev/null
+++ b/.changeset/smart-ears-invent.md
@@ -0,0 +1,5 @@
+---
+'@sveltejs/vite-plugin-svelte': patch
+---
+
+fix(prebundleSvelteLibraries): don't try to append missing sourcemap
diff --git a/packages/vite-plugin-svelte/src/utils/esbuild.js b/packages/vite-plugin-svelte/src/utils/esbuild.js
index 355934832..ac49fd7bb 100644
--- a/packages/vite-plugin-svelte/src/utils/esbuild.js
+++ b/packages/vite-plugin-svelte/src/utils/esbuild.js
@@ -106,5 +106,7 @@ async function compileSvelte(options, { filename, code }, statsCollection) {
 	if (endStat) {
 		endStat();
 	}
-	return compiled.js.code + '//# sourceMappingURL=' + compiled.js.map.toUrl();
+	return compiled.js.map
+		? compiled.js.code + '//# sourceMappingURL=' + compiled.js.map.toUrl()
+		: compiled.js.code;
 }