gistfile1.txt

diff --git a/lib/gauche/process.scm b/lib/gauche/process.scm
index 069348e..683ab6e 100644
--- a/lib/gauche/process.scm
+++ b/lib/gauche/process.scm
@@ -382,6 +382,7 @@
             [gauche.sys.threads
              (receive (in out) (sys-pipe)
                (push! iomap `(,fd . ,in))
+               (push! toclose in)
                (thread-start! (make-thread (cut write-arg out))))]
             [else
              ;; If we can't use threads, we fall back to using temporary