diff --git a/fwdpy11/conditional_models/_track_added_mutation.py b/fwdpy11/conditional_models/_track_added_mutation.py
index 3ac3f8ea0..a4307fe7c 100644
--- a/fwdpy11/conditional_models/_track_added_mutation.py
+++ b/fwdpy11/conditional_models/_track_added_mutation.py
@@ -82,12 +82,12 @@ def __call__(
     ) -> SimulationStatus:
         if pop.generation == self.until:
             if pop.mutations[index].key != key and self.is_fixed(pop, key) is False:
-                return SimulationStatus(True, False)
+                return SimulationStatus.Restart
             if pop.mcounts[index] > 0:
-                return SimulationStatus(False, True)
+                return SimulationStatus.Complete
             if self.is_fixed(pop, key):
-                return SimulationStatus(False, True)
-        return SimulationStatus(False, False)
+                return SimulationStatus.Complete
+        return SimulationStatus.Continue
 
 
 @attr.s(auto_attribs=True)