diff --git a/lib/scope.js b/lib/scope.js
index a8e89954..ddefdedd 100644
--- a/lib/scope.js
+++ b/lib/scope.js
@@ -132,6 +132,7 @@ function defineScope(cls, targetClass, name, params, methods) {
     }
 
     function mergeParams(base, update) {
+        base = base || {};
         if (update.where) {
             base.where = merge(base.where, update.where);
         }