From 701670c9a6daaac76f588481698b576bb4d6505d Mon Sep 17 00:00:00 2001
From: Jeffrey Posnick <jeffy@google.com>
Date: Thu, 7 Nov 2019 15:29:19 -0500
Subject: [PATCH] Correct a parameter typing (#2275)

---
 packages/workbox-navigation-preload/src/enable.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/workbox-navigation-preload/src/enable.ts b/packages/workbox-navigation-preload/src/enable.ts
index 5ac34c371..5f5c7c7d0 100644
--- a/packages/workbox-navigation-preload/src/enable.ts
+++ b/packages/workbox-navigation-preload/src/enable.ts
@@ -24,7 +24,7 @@ declare var self: ServiceWorkerGlobalScope;
  *
  * @memberof workbox.navigationPreload
  */
-function enable(headerValue: string) {
+function enable(headerValue?: string) {
   if (isSupported()) {
     self.addEventListener('activate', (event: ExtendableEvent) => {
       event.waitUntil(