diff --git a/basis/io/backend/unix/unix.factor b/basis/io/backend/unix/unix.factor
index c4883f54ef..4bc8868a3c 100644
--- a/basis/io/backend/unix/unix.factor
+++ b/basis/io/backend/unix/unix.factor
@@ -167,7 +167,7 @@ M: stdin refill
 M: unix (init-stdio)
     <stdin> <input-port>
     1 <fd> <output-port>
-    2 <fd> <output-port> ;
+    2 <fd> <output-port> t ;
 
 ! mx io-task for embedding an fd-based mx inside another mx
 TUPLE: mx-port < port mx ;