diff --git a/tests/letstest/multitester.py b/tests/letstest/multitester.py
index 1cd11b028..716426a85 100644
--- a/tests/letstest/multitester.py
+++ b/tests/letstest/multitester.py
@@ -552,6 +552,7 @@ try:
         p.join(timeout)
         while p.is_alive():
             print('Waiting on client processes...')
+            sys.stdout.flush()
             p.join(timeout)
     # add SENTINEL to output queue
     outqueue.put(SENTINEL)