diff --git a/gnu/packages/lsof.scm b/gnu/packages/lsof.scm
index 311e244608..e29f3b4569 100644
--- a/gnu/packages/lsof.scm
+++ b/gnu/packages/lsof.scm
@@ -2,7 +2,7 @@
 ;;; Copyright © 2013 Andreas Enge <andreas@enge.fr>
 ;;; Copyright © 2017 Efraim Flashner <efraim@flashner.co.il>
 ;;; Copyright © 2018 Tobias Geerinckx-Rice <me@tobias.gr>
-;;; Copyright © 2018 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2018, 2019 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -69,6 +69,13 @@ (define-public lsof
           (lambda _
             (setenv "LSOF_CC" "gcc")
             (setenv "LSOF_MAKE" "make")
+
+            ;; By default, the makefile captures the output of 'uname -a'.
+            ;; Provide a fixed output instead to make builds reproducible.
+            (setenv "LSOF_SYSINFO"
+                    (string-append "GNU/" (utsname:sysname (uname))
+                                   " (GNU Guix)"))
+
             (invoke "./Configure" "linux")
             #t))
         (add-after 'configure 'patch-timestamps