diff --git a/src/core.js b/src/core.js
index d4dad72..15068b0 100644
--- a/src/core.js
+++ b/src/core.js
@@ -625,7 +625,7 @@ function requestHandler(req, res, next) {
 }
 
 function init(config) {
-  coreConfig = config;
+  if (config) coreConfig = config;
   return requestHandler;
 }