diff --git a/.changeset/fine-pens-attend.md b/.changeset/fine-pens-attend.md
new file mode 100644
index 000000000000..127db0f08334
--- /dev/null
+++ b/.changeset/fine-pens-attend.md
@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+fix: ensure static error page is loaded correctly for custom user errors
diff --git a/packages/kit/src/runtime/server/utils.js b/packages/kit/src/runtime/server/utils.js
index 880e966e99f1..e0889361dbe9 100644
--- a/packages/kit/src/runtime/server/utils.js
+++ b/packages/kit/src/runtime/server/utils.js
@@ -98,7 +98,8 @@ export async function handle_fatal_error(event, options, error) {
  */
 export async function handle_error_and_jsonify(event, options, error) {
 	if (error instanceof HttpError) {
-		return error.body;
+		// @ts-expect-error custom user errors may not have a message field if App.Error is overwritten
+		return { message: 'Unknown Error', ...error.body };
 	}
 
 	if (__SVELTEKIT_DEV__ && typeof error == 'object') {