diff --git a/nix/sources.nix b/nix/sources.nix
index 8a725cb..0ad45ef 100644
--- a/nix/sources.nix
+++ b/nix/sources.nix
@@ -7,13 +7,13 @@ let
   #
 
   fetch_file = pkgs: spec:
-    if spec.builtin or true then
+    if spec.builtin or false then
       builtins_fetchurl { inherit (spec) url sha256; }
     else
       pkgs.fetchurl { inherit (spec) url sha256; };
 
   fetch_tarball = pkgs: spec:
-    if spec.builtin or true then
+    if spec.builtin or false then
       builtins_fetchTarball { inherit (spec) url sha256; }
     else
       pkgs.fetchzip { inherit (spec) url sha256; };