diff --git a/guix/utils.scm b/guix/utils.scm
index fb962df8ba..3fefa49607 100644
--- a/guix/utils.scm
+++ b/guix/utils.scm
@@ -155,7 +155,7 @@ (define (decompressed-port compression input)
   (match compression
     ((or #f 'none) (values input '()))
     ('bzip2        (filtered-port `(,%bzip2 "-dc") input))
-    ('xz           (filtered-port `(,%xz "-dc -T0") input))
+    ('xz           (filtered-port `(,%xz "-dc" "-T0") input))
     ('gzip         (filtered-port `(,%gzip "-dc") input))
     (else          (error "unsupported compression scheme" compression))))
 
@@ -165,7 +165,7 @@ (define (compressed-port compression input)
   (match compression
     ((or #f 'none) (values input '()))
     ('bzip2        (filtered-port `(,%bzip2 "-c") input))
-    ('xz           (filtered-port `(,%xz "-c -T0") input))
+    ('xz           (filtered-port `(,%xz "-c" "-T0") input))
     ('gzip         (filtered-port `(,%gzip "-c") input))
     (else          (error "unsupported compression scheme" compression))))
 
@@ -222,7 +222,7 @@ (define* (compressed-output-port compression output
   (match compression
     ((or #f 'none) (values output '()))
     ('bzip2        (filtered-output-port `(,%bzip2 "-c" ,@options) output))
-    ('xz           (filtered-output-port `(,%xz "-c -T0" ,@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))))