diff --git a/config.py b/config.py
index 7cb0ed2ba5..9b48185134 100644
--- a/config.py
+++ b/config.py
@@ -222,6 +222,8 @@ def _checksd_path(directory):
 
 
 def _is_affirmative(s):
+    if s is None:
+        return False
     # int or real bool
     if isinstance(s, int):
         return bool(s)