diff --git a/lib/helpers.js b/lib/helpers.js
index 985ca39..cb1052a 100644
--- a/lib/helpers.js
+++ b/lib/helpers.js
@@ -177,7 +177,7 @@ function store_images(rid, userId, cache_details, type, callback) {
             // an error occured, not caching. we can try in 60 seconds
             callback_for(userId, "skin", store_err, null);
           } else {
-            cache.save_hash(rid, userId, skin_hash, null, function(cache_err) {
+            cache.save_hash(rid, userId, skin_hash, undefined, function(cache_err) {
               callback_for(userId, "skin", (store_err || cache_err), skin_hash);
             });
           }