diff --git a/.changeset/slimy-cows-listen.md b/.changeset/slimy-cows-listen.md
new file mode 100644
index 000000000000..adfca8dadc90
--- /dev/null
+++ b/.changeset/slimy-cows-listen.md
@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+fix: make param matchers generated type import end with `.js`
diff --git a/packages/kit/src/core/sync/write_types/index.js b/packages/kit/src/core/sync/write_types/index.js
index 42728feaf187..e57b00183e6f 100644
--- a/packages/kit/src/core/sync/write_types/index.js
+++ b/packages/kit/src/core/sync/write_types/index.js
@@ -585,7 +585,7 @@ function replace_ext_with_js(file_path) {
 function generate_params_type(params, outdir, config) {
 	/** @param {string} matcher */
 	const path_to_matcher = (matcher) =>
-		posixify(path.relative(outdir, path.join(config.kit.files.params, matcher)));
+		posixify(path.relative(outdir, path.join(config.kit.files.params, matcher + '.js')));
 
 	return `{ ${params
 		.map(