diff --git a/concurrencytest.py b/concurrencytest.py
index 058c054..758a148 100644
--- a/concurrencytest.py
+++ b/concurrencytest.py
@@ -69,7 +69,7 @@ def do_fork(suite):
             pid = os.fork()
             if pid == 0:
                 try:
-                    stream = os.fdopen(c2pwrite, 'wb', 1)
+                    stream = os.fdopen(c2pwrite, 'wb')
                     os.close(c2pread)
                     # Leave stderr and stdout open so we can see test noise
                     # Close stdin so that the child goes away if it decides to
@@ -93,7 +93,7 @@ def do_fork(suite):
                 os._exit(0)
             else:
                 os.close(c2pwrite)
-                stream = os.fdopen(c2pread, 'rb', 1)
+                stream = os.fdopen(c2pread, 'rb')
                 test = ProtocolTestCase(stream)
                 result.append(test)
         return result