diff --git a/cortex/webgl/serve.py b/cortex/webgl/serve.py
index b0baec8ea..f5af29977 100644
--- a/cortex/webgl/serve.py
+++ b/cortex/webgl/serve.py
@@ -351,6 +351,8 @@ def __getattr__(self, attr):
             return self.attrs[attr][1]
 
     def __setattr__(self, attr, value):
+        if hasattr(self, "attrs") and self.attrs is None:
+            return super(JSProxy, self).__setattr__(attr, value)
         if not hasattr(self, "attrs") or attr not in self.attrs:
             return super(JSProxy, self).__setattr__(attr, value)