diff --git a/cps/server.py b/cps/server.py
index 45673102..14ab0c37 100644
--- a/cps/server.py
+++ b/cps/server.py
@@ -153,7 +153,7 @@ class WebServer(object):
         # The value of __package__ indicates how Python was called. It may
         # not exist if a setuptools script is installed as an egg. It may be
         # set incorrectly for entry points created with pip on Windows.
-        if getattr(__main__, "__package__", "") == "" or (
+        if getattr(__main__, "__package__", "") in ["", None] or (
             os.name == "nt"
             and __main__.__package__ == ""
             and not os.path.exists(py_script)