diff --git a/js/sweph.js b/js/sweph.js
index 3b1d46e..7ebfd45 100644
--- a/js/sweph.js
+++ b/js/sweph.js
@@ -9,6 +9,12 @@ self.Module = {
     }
 };
 
+self.NProgress = self.NProgress || {
+    start: function () {},
+    set: function () {},
+    done: function () {}
+};
+
 self.importScripts("pmom.js");
 
 self.data = {};