diff --git a/Lib/concurrent/futures/process.py b/Lib/concurrent/futures/process.py
index ff566d3..8082940 100644
--- a/Lib/concurrent/futures/process.py
+++ b/Lib/concurrent/futures/process.py
@@ -232,6 +232,7 @@
                 # X.
                 for p in processes:
                     p.join()
+                call_queue.close()
                 return
             else:
                 # Start shutting down by telling a process it can exit.