diff --git a/roles/captiveportal/files/capture-wsgi.py b/roles/captiveportal/files/capture-wsgi.py
index d6d3a5b26..7362fc308 100755
--- a/roles/captiveportal/files/capture-wsgi.py
+++ b/roles/captiveportal/files/capture-wsgi.py
@@ -453,7 +453,7 @@ def application (environ, start_response):
       status = '200 OK'
       headers = [('Content-type', 'text/html')]
       start_response(status, headers)
-      return [""]
+      return [b""]
 
    #### parse OS platform based upon URL  ##################
    # mac