diff --git a/pipe_io_server/pipe_io_server.py b/pipe_io_server/pipe_io_server.py
index 1553999..9d28083 100644
--- a/pipe_io_server/pipe_io_server.py
+++ b/pipe_io_server/pipe_io_server.py
@@ -7,7 +7,7 @@ from .terminate_process_on_failure import terminate_process_on_failure
 
 
 class PipeIOServer(Thread):
-    def __init__(self, in_pipe=None, out_pipe=None, permissions=0o600):
+    def __init__(self, in_pipe, out_pipe, permissions=0o600):
         super().__init__(daemon=True)
         self._in_pipe, self._out_pipe = in_pipe, out_pipe
         self._create_pipes(permissions)