diff --git a/_msprimemodule.c b/_msprimemodule.c
index 6f384b30f..0ff979e3b 100644
--- a/_msprimemodule.c
+++ b/_msprimemodule.c
@@ -2861,6 +2861,7 @@ Simulator_parse_demographic_events(Simulator *self, PyObject *py_events)
     Py_XDECREF(instantaneous_bottleneck_s);
     Py_XDECREF(initial_size_s);
     Py_XDECREF(growth_rate_s);
+    Py_XDECREF(census_event_s);
     return ret;
 }