diff --git a/validator/sawtooth_validator/execution/executor.py b/validator/sawtooth_validator/execution/executor.py
index <HASH>..<HASH> 100644
--- a/validator/sawtooth_validator/execution/executor.py
+++ b/validator/sawtooth_validator/execution/executor.py
@@ -296,7 +296,7 @@ class _Waiter(object):
         # Wait for the processor type to be registered
         self._processors.cancellable_wait(
             processor_type=self._processor_type,
-            is_cancelled=self._cancelled_event)
+            cancelled_event=self._cancelled_event)
 
         if self._cancelled_event.is_set():
             LOGGER.info("waiting cancelled on %s", self._processor_type)
Fix incorrect keyword argument

The TypeError on invalid keyword argument wasn't displayed due to
running in a threadpool.