diff --git a/lang/rust/src/registry.sld b/lang/rust/src/registry.sld
index 5275a93..0344c8c 100644
--- a/lang/rust/src/registry.sld
+++ b/lang/rust/src/registry.sld
@@ -140,10 +140,11 @@
      (define url (string-append "https://static.crates.io/crates/" (lockfile-entry-name lockfile-entry) "/" (lockfile-entry-version lockfile-entry) "/download"))
      (define crate-name (string-append (lockfile-entry-name lockfile-entry) "-" (lockfile-entry-version lockfile-entry) ".crate"))
      (define crate-name-path (string-append (lockfile-entry-name lockfile-entry) "-" (lockfile-entry-version lockfile-entry)))
-     (define fetched-tarball (store-path-for-fod crate-name "builtin" '("builtin:fetchurl") `(("url" . ,url)) "sha256" (lockfile-entry-checksum lockfile-entry) #f))
+     (define fetched-tarball (store-path-for-fod crate-name "builtin" '("builtin:fetchurl") `(("url" . ,url) ("allowSubstitutes" . "")) "sha256" (lockfile-entry-checksum lockfile-entry) #f))
      (define unpacked-tarball
        (cdar (store-path-for-drv crate-name "builtin" '("builtin:unpack-channel")
               #~(("src" . #$fetched-tarball)
+                 ("allowSubstitutes" . "")
                  ("channelName" . #$crate-name-path)) '("out"))))
      #~,(string-append #$unpacked-tarball "/" #$crate-name-path))