diff --git a/loopx/control_plane/collaboration/peers.py b/loopx/control_plane/collaboration/peers.py
index e0cebe3d48..160a7c0742 100644
--- a/loopx/control_plane/collaboration/peers.py
+++ b/loopx/control_plane/collaboration/peers.py
@@ -531,7 +531,7 @@ def input_readiness(
                 # Nonblocking open plus fstat prevents a FIFO/device reference
                 # from hanging the worker's entire Inbox read.
                 with os.fdopen(
-                    os.open(path, os.O_RDONLY | os.O_NONBLOCK), "rb"
+                    os.open(path, os.O_RDONLY | getattr(os, "O_NONBLOCK", 0)), "rb"
                 ) as stream:
                     if not stat.S_ISREG(os.fstat(stream.fileno()).st_mode):
                         raise OSError("input is not a regular file")