diff --git a/templates/src/server/middleware/get_page_handler.ts b/templates/src/server/middleware/get_page_handler.ts
index 802ee0f..847e876 100644
--- a/templates/src/server/middleware/get_page_handler.ts
+++ b/templates/src/server/middleware/get_page_handler.ts
@@ -104,7 +104,7 @@ export function get_page_handler(
 					);
 
 					if (include_cookies) {
-						if (!opts.headers) opts.headers = {};
+						opts.headers = Object.assign({}, opts.headers);
 
 						const cookies = Object.assign(
 							{},