diff --git a/src/core/index.js b/src/core/index.js
index 49f8bb31..8f3f4844 100644
--- a/src/core/index.js
+++ b/src/core/index.js
@@ -24,6 +24,7 @@ module.exports = function SwaggerUI(opts) {
     spec: {},
     url: "",
     layout: "BaseLayout",
+    docExpansion: "list",
     validatorUrl: "https://online.swagger.io/validator",
     configs: {},
     custom: {},