diff --git a/out-of-tree/nixGL/fetch.py b/out-of-tree/nixGL/fetch.py
index a152704..11d0e3e 100755
--- a/out-of-tree/nixGL/fetch.py
+++ b/out-of-tree/nixGL/fetch.py
@@ -41,10 +41,6 @@ def req_monad(url: str, err_fn, then_fn):
     return then_fn(res.data)
 
 identity = lambda e: e
-def _fail(msg: str|None=None):
-    if msg:
-        assert False, msg
-    assert False
 none_id = lambda _: None
 
 def get_sha256(version: str) -> str | None:
diff --git a/out-of-tree/nixGL/nixGL.nix b/out-of-tree/nixGL/nixGL.nix
index dfaaf11..8dd24ed 100644
--- a/out-of-tree/nixGL/nixGL.nix
+++ b/out-of-tree/nixGL/nixGL.nix
@@ -56,12 +56,13 @@ let
         done
       '';
     };
+  fetch_db = builtins.fromJSON (builtins.readFile ./nvidia_versions.json);
   top = rec {
     /*
       It contains the builder for different nvidia configuration, parametrized by
       the version of the driver and sha256 sum of the driver installer file.
     */
-    nvidiaPackages = { version }:
+    nvidiaPackages = { version, sha256? fetch_db."${version}".sha256 }:
       let
         nvidiaDrivers = (linuxPackages.nvidia_x11.override { }).overrideAttrs
           (oldAttrs: {
diff --git a/nvidia_versions.json b/out-of-tree/nixGL/nvidia_versions.json
similarity index 100%
rename from nvidia_versions.json
rename to out-of-tree/nixGL/nvidia_versions.json