diff --git a/gnu/system/uuid.scm b/gnu/system/uuid.scm
index f13960c3e9..e7a3a0439d 100644
--- a/gnu/system/uuid.scm
+++ b/gnu/system/uuid.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2016, 2017, 2018 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2016, 2017, 2018, 2019 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2017 Danny Milosavljevic <dannym@scratchpost.org>
 ;;;
 ;;; This file is part of GNU Guix.
@@ -175,7 +175,7 @@ (define (fat-uuid->string uuid)
   "Convert FAT32/FAT16 UUID, a 4-byte bytevector, to its string representation."
   (let ((high  (bytevector-uint-ref uuid 0 %fat-endianness 2))
         (low (bytevector-uint-ref uuid 2 %fat-endianness 2)))
-    (format #f "~:@(~x-~x~)" low high)))
+    (format #f "~:@(~4,'0x-~4,'0x~)" low high)))
 
 (define %fat-uuid-rx
   (make-regexp "^([[:xdigit:]]{4})-([[:xdigit:]]{4})$"))
diff --git a/tests/uuid.scm b/tests/uuid.scm
index 260614f079..1c6d1e9e57 100644
--- a/tests/uuid.scm
+++ b/tests/uuid.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2015, 2017, 2018 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2015, 2017, 2018, 2019 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -57,6 +57,10 @@ (define-module (test-uuid)
   "1234-ABCD"
   (uuid->string (uuid "1234-abcd" 'fat32)))
 
+(test-equal "uuid, FAT32, leading zeros preserved"
+  "00CA-050E"                                    ;<https://bugs.gnu.org/35582>
+  (uuid->string (uuid "00CA-050E" 'fat32)))
+
 (test-assert "uuid, dynamic value"
   (let* ((good "4dab5feb-d176-45de-b287-9b0a6e4c01cb")
          (bad  (string-drop good 3)))