diff --git a/lib/index.js b/lib/index.js
index 2e474b7..ac62bf6 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -155,11 +155,9 @@ GitStats.iterateDays = function (data, callback) {
     }
 
     // Merge the defaults
-    data = Ul.merge(data, {
-        end: Moment()
-      , start: Moment().subtract(1, "years")
-      , format: DATE_FORMAT
-    });
+    data.end = data.end || Moment();
+    data.start = data.start || Moment().subtract(1, "years");
+    data.format = data.format || DATE_FORMAT;
 
     var start = data.start
       , end = data.end