diff --git a/src/Filters/Rules/Person/_IsMoreThanNthGenerationDescendantOf.py b/src/Filters/Rules/Person/_IsMoreThanNthGenerationDescendantOf.py
index 47ba26309..ac6ba626b 100644
--- a/src/Filters/Rules/Person/_IsMoreThanNthGenerationDescendantOf.py
+++ b/src/Filters/Rules/Person/_IsMoreThanNthGenerationDescendantOf.py
@@ -60,7 +60,7 @@ class IsMoreThanNthGenerationDescendantOf(Rule):
             pass
 
     def reset(self):
-        self.map.reset()
+        self.map.clear()
 
     def apply(self,db,person):
         return person.handle in self.map