Fix Config.unset() making the name known
diff --git a/scripts/config.py b/scripts/config.py
index aaea484..81c35d0 100755
--- a/scripts/config.py
+++ b/scripts/config.py
@@ -131,9 +131,10 @@
     def unset(self, name):
         """Make name unset (inactive).
 
-        name remains known.
+        name remains known if it was known before.
         """
-        self.set(name)
+        if name not in self.settings:
+            return
         self.settings[name].active = False
 
     def adapt(self, adapter):