diff --git a/guix/import/github.scm b/guix/import/github.scm
index df5a6b0e08..1e0bb53d9a 100644
--- a/guix/import/github.scm
+++ b/guix/import/github.scm
@@ -32,10 +32,13 @@
 
 (define (json-fetch* url)
   "Return a representation of the JSON resource URL (a list or hash table), or
-#f if URL returns 404."
+#f if URL returns 403 or 404."
   (guard (c ((and (http-get-error? c)
-                  (= 404 (http-get-error-code c)))
-             #f))                       ;"expected" if package is unknown
+                  (let ((error (http-get-error-code c)))
+                    (or (= 403 error)
+                        (= 404 error))))
+             #f))     ;; "expected" if there is an authentification error (403),
+                      ;; or if package is unknown (404).
     ;; Note: github.com returns 403 if we omit a 'User-Agent' header.
     (let* ((port   (http-fetch url))
            (result (json->scm port)))