diff --git a/guix/hg-download.scm b/guix/hg-download.scm
index bd55946523..c6cee2dbb8 100644
--- a/guix/hg-download.scm
+++ b/guix/hg-download.scm
@@ -65,6 +65,12 @@ HASH-ALGO (a symbol).  Use NAME as the file name, or a generic name if #f."
   (define guile-zlib
     (module-ref (resolve-interface '(gnu packages guile)) 'guile-zlib))
 
+  (define guile-json
+    (module-ref (resolve-interface '(gnu packages guile)) 'guile-json-4))
+
+  (define gnutls
+    (module-ref (resolve-interface '(gnu packages tls)) 'gnutls))
+
   (define modules
     (delete '(guix config)
             (source-module-closure '((guix build hg)
@@ -72,7 +78,8 @@ HASH-ALGO (a symbol).  Use NAME as the file name, or a generic name if #f."
 
   (define build
     (with-imported-modules modules
-      (with-extensions (list guile-zlib)
+      (with-extensions (list guile-json gnutls ;for (guix swh)
+                             guile-zlib)
         #~(begin
             (use-modules (guix build hg)
                          (guix build download-nar))