diff --git a/morss/morss.py b/morss/morss.py
index cb340b4..0d34bae 100644
--- a/morss/morss.py
+++ b/morss/morss.py
@@ -696,7 +696,7 @@ def cgi_app(environ, start_response):
 
 def cgi_wrapper(environ, start_response):
 	try:
-		return cgi_app(environ, start_response)
+		return cgi_app(environ, start_response) or []
 	except (KeyboardInterrupt, SystemExit):
 		raise
 	except MorssException as e: