diff --git a/src/util-io.scm b/src/util-io.scm
index 652acaa..ae71937 100644
--- a/src/util-io.scm
+++ b/src/util-io.scm
@@ -74,6 +74,7 @@
 	 (display (car lines) stdin)
 	 (newline stdin)
 	 (loop (cdr lines))))
+     (close-output-port stdin)
      (let ((result (read-lines stdout)))
        (let-values (((pid exit-ok? exit/signal) (process-wait pid)))
 	 result))))