diff --git a/guix/utils.scm b/guix/utils.scm
index de4aa6531..2cf9be36d 100644
--- a/guix/utils.scm
+++ b/guix/utils.scm
@@ -153,9 +153,11 @@ buffered data is lost."
                   (close-port in)
                   (dump-port input out))
                 (lambda ()
+                  (close-port input)
                   (false-if-exception (close out))
                   (primitive-_exit 0))))
              (child
+              (close-port input)
               (close-port out)
               (loop in (cons child pids)))))))))