diff --git a/public/js/wn/misc/utils.js b/public/js/wn/misc/utils.js
index 479d98ca0b..c4075a6b31 100644
--- a/public/js/wn/misc/utils.js
+++ b/public/js/wn/misc/utils.js
@@ -170,6 +170,6 @@ wn.utils = {
 	},
 	
 	sum: function(list) {
-		return list.reduce(function(previous_value, current_value) { return flt(previous_value) + flt(current_value); });
+		return list.reduce(function(previous_value, current_value) { return flt(previous_value) + flt(current_value); }, 0.0);
 	},
 };
\ No newline at end of file