diff --git a/guix/scripts/pack.scm b/guix/scripts/pack.scm
index 626c592e1c..9e91bc22ac 100644
--- a/guix/scripts/pack.scm
+++ b/guix/scripts/pack.scm
@@ -1,5 +1,6 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2015, 2017 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2017 Efraim Flashner <efraim@flashner.co.il>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -59,7 +60,7 @@
         (compressor "lzip"  "lz"
                     #~(#+(file-append lzip "/bin/lzip") "-9"))
         (compressor "xz"    "xz"
-                    #~(#+(file-append xz "/bin/xz") "-e"))
+                    #~(#+(file-append xz "/bin/xz") "-e -T0"))
         (compressor "bzip2" "bz2"
                     #~(#+(file-append bzip2 "/bin/bzip2") "-9"))))
 
diff --git a/guix/utils.scm b/guix/utils.scm
index bc90686de0..fb962df8ba 100644
--- a/guix/utils.scm
+++ b/guix/utils.scm
@@ -5,6 +5,7 @@
 ;;; Copyright © 2014 Ian Denhardt <ian@zenhack.net>
 ;;; Copyright © 2016 Mathieu Lirzin <mthl@gnu.org>
 ;;; Copyright © 2015 David Thompson <davet@gnu.org>
+;;; Copyright © 2017 Efraim Flashner <efraim@flashner.co.il>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -154,7 +155,7 @@ a symbol such as 'xz."
   (match compression
     ((or #f 'none) (values input '()))
     ('bzip2        (filtered-port `(,%bzip2 "-dc") input))
-    ('xz           (filtered-port `(,%xz "-dc") input))
+    ('xz           (filtered-port `(,%xz "-dc -T0") input))
     ('gzip         (filtered-port `(,%gzip "-dc") input))
     (else          (error "unsupported compression scheme" compression))))
 
@@ -164,7 +165,7 @@ a symbol such as 'xz."
   (match compression
     ((or #f 'none) (values input '()))
     ('bzip2        (filtered-port `(,%bzip2 "-c") input))
-    ('xz           (filtered-port `(,%xz "-c") input))
+    ('xz           (filtered-port `(,%xz "-c -T0") input))
     ('gzip         (filtered-port `(,%gzip "-c") input))
     (else          (error "unsupported compression scheme" compression))))
 
@@ -221,7 +222,7 @@ program--e.g., '(\"--fast\")."
   (match compression
     ((or #f 'none) (values output '()))
     ('bzip2        (filtered-output-port `(,%bzip2 "-c" ,@options) output))
-    ('xz           (filtered-output-port `(,%xz "-c" ,@options) output))
+    ('xz           (filtered-output-port `(,%xz "-c -T0" ,@options) output))
     ('gzip         (filtered-output-port `(,%gzip "-c" ,@options) output))
     (else          (error "unsupported compression scheme" compression))))