diff --git a/paramecio2/libraries/mtemplates.py b/paramecio2/libraries/mtemplates.py
index bf6b9b9..711d07d 100644
--- a/paramecio2/libraries/mtemplates.py
+++ b/paramecio2/libraries/mtemplates.py
@@ -69,6 +69,8 @@ class PTemplate:
     def add_js(self, js, module=''):
         if not js in self.js:
             self.js[js]='<script language="Javascript" src="{}"></script>'.format(make_media_url('js/'+js, module))
+            
+        return ""
         
     def load_js(self):