diff --git a/isso/wsgi.py b/isso/wsgi.py
index 1788d47..60c1a58 100644
--- a/isso/wsgi.py
+++ b/isso/wsgi.py
@@ -84,6 +84,8 @@ def origin(hosts):
     hosts = [urlsplit(h) for h in hosts]
 
     def func(environ):
+        if 'ISSO_CORS_ORIGIN' in environ:
+            return environ['ISSO_CORS_ORIGIN']
 
         if not hosts:
             return "http://invalid.local"