diff --git a/scam.py b/scam.py
index 1ce104e..66118b1 100755
--- a/scam.py
+++ b/scam.py
@@ -301,6 +301,11 @@ class MainPanel(wx.Panel):
     def on_change(self, event):
         old_cfg = self.orig_cfg
         new_cfg = self.make_cfg()
+
+        for k, v in KNOWN_TYPES.items():
+            if new_cfg.get(k) is None:
+                new_cfg[k] = v
+
         color = wx.Colour(164, 36, 23) if new_cfg != old_cfg else wx.NullColour
         self.btn_save.SetBackgroundColour(color)