diff --git a/invoke/runners.py b/invoke/runners.py
index 281fe546..f7ca4f00 100644
--- a/invoke/runners.py
+++ b/invoke/runners.py
@@ -498,6 +498,7 @@ def _finish(self):
         # upset and aborted execution; make a generic Failure out of it and
         # raise that.
         if watcher_errors:
+            self.kill()
             # TODO: ambiguity exists if we somehow get WatcherError in *both*
             # threads...as unlikely as that would normally be.
             raise Failure(result, reason=watcher_errors[0])