diff --git a/openmc/tallies.py b/openmc/tallies.py
index 4ea713092f3..4ca54c6084e 100644
--- a/openmc/tallies.py
+++ b/openmc/tallies.py
@@ -301,6 +301,8 @@ def estimator(self):
 
     @estimator.setter
     def estimator(self, estimator):
+        if estimator is None:
+            self._estimator = None
         cv.check_value('estimator', estimator, ESTIMATOR_TYPES)
         self._estimator = estimator