diff --git a/guix/build-system/r.scm b/guix/build-system/r.scm
index 2c8a89f8de..6bdb7061eb 100644
--- a/guix/build-system/r.scm
+++ b/guix/build-system/r.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2015 Ricardo Wurmus <rekado@elephly.net>
+;;; Copyright © 2015, 2017 Ricardo Wurmus <rekado@elephly.net>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -50,8 +50,11 @@ (define (cran-uri name version)
 (define (bioconductor-uri name version)
   "Return a URI string for the R package archive on Bioconductor for the
 release corresponding to NAME and VERSION."
-  (string-append "https://bioconductor.org/packages/release/bioc/src/contrib/"
-                 name "_" version ".tar.gz"))
+  (list (string-append "https://bioconductor.org/packages/release/bioc/src/contrib/"
+                       name "_" version ".tar.gz")
+        ;; TODO: use %bioconductor-version from (guix import cran)
+        (string-append "https://bioconductor.org/packages/3.6/bioc/src/contrib/Archive/"
+                       name "_" version ".tar.gz")))
 
 (define %r-build-system-modules
   ;; Build-side modules imported by default.
diff --git a/guix/import/cran.scm b/guix/import/cran.scm
index 5622f759e0..ec2b7e6029 100644
--- a/guix/import/cran.scm
+++ b/guix/import/cran.scm
@@ -182,7 +182,7 @@ (define (fetch-description repository name)
      ;; package's DESCRIPTION file over HTTP, so we determine the version,
      ;; download the source tarball, and then extract the DESCRIPTION file.
      (let* ((version (latest-bioconductor-package-version name))
-            (url     (bioconductor-uri name version))
+            (url     (car (bioconductor-uri name version)))
             (tarball (with-store store (download-to-store store url))))
        (call-with-temporary-directory
         (lambda (dir)
@@ -469,7 +469,7 @@ (define version
        (upstream-source
         (package (package-name package))
         (version version)
-        (urls (list (bioconductor-uri upstream-name version))))))
+        (urls (bioconductor-uri upstream-name version)))))
 
 (define (cran-package? package)
   "Return true if PACKAGE is an R package from CRAN."