diff --git a/gnu/build/file-systems.scm b/gnu/build/file-systems.scm
index 4ac7a7f8c66279b490e52e479fcbacc3f0e29f99..84f58538fda9f0a949c298379e62dc23de4e988b 100644
--- a/gnu/build/file-systems.scm
+++ b/gnu/build/file-systems.scm
@@ -293,7 +293,7 @@ (define* (mount-file-system spec #:key (root "/root"))
        (mkdir-p (string-append root "/etc"))
        (let ((port (open-file (string-append root "/etc/mtab") "a")))
          (format port "~a ~a ~a ~a 0 0~%"
-                 source mount-point type (or options ""))
+                 source mount-point type (or options "rw"))
          (close-port port))))))
 
 ;;; file-systems.scm ends here