diff --git a/flake.lock b/flake.lock
index fa32e81..69a466a 100644
--- a/flake.lock
+++ b/flake.lock
@@ -17,16 +17,18 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1632570486,
-        "narHash": "sha256-1CPYfW5dgquaizUwJPtCL+9xu1peHWixLN2DI62oJoQ=",
-        "owner": "NixOS",
+        "lastModified": 1636723036,
+        "narHash": "sha256-zFuu3TTj/NLq3NPJ8pprlmkOpjAoW3AWQNac3UFkCG8=",
+        "owner": "nixos",
         "repo": "nixpkgs",
-        "rev": "f05a99e116df08af551c7c49e7d4aa4020d43acd",
+        "rev": "50a1ef0f59752623af884f5085e3d5e8bd806c77",
         "type": "github"
       },
       "original": {
-        "id": "nixpkgs",
-        "type": "indirect"
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "50a1ef0f59752623af884f5085e3d5e8bd806c77",
+        "type": "github"
       }
     },
     "nixpkgs_2": {
diff --git a/flake.nix b/flake.nix
index 3f8688d..bc417ad 100644
--- a/flake.nix
+++ b/flake.nix
@@ -3,6 +3,8 @@
 
   inputs.rust.url = "github:oxalica/rust-overlay";
 
+  inputs.nixpkgs.url = "github:nixos/nixpkgs/50a1ef0f59752623af884f5085e3d5e8bd806c77";
+
   outputs = { self, nixpkgs, rust }:
     let
       forEachSystem = nixpkgs.lib.genAttrs [ "aarch64-linux" "x86_64-linux" ];
diff --git a/preserves-nim/default.nix b/preserves-nim/default.nix
index d0d42bb..83cc0f1 100644
--- a/preserves-nim/default.nix
+++ b/preserves-nim/default.nix
@@ -1,38 +1,34 @@
-{ lib, nimPackages, fetchFromGitea }:
+{ lib, nimPackages, fetchFromGitea, fetchFromGitHub }:
 with nimPackages;
 
 let
-  bigints = fetchNimble {
-    pname = "bigints";
-    version = "0.5.0";
-    hash = "sha256-zMTXXC0lYVzXaKl8eC/SA/CymRgovgzxBdvEn1VE9p0=";
+  compiler = fetchFromGitHub {
+    owner = "nim-lang";
+    repo = "nim";
+    rev = "v1.6.0";
+    hash = "sha256-C9oveXIufv0HqMQw6eNmLbku4Sd7r28PKcRILvKYzn0=";
   };
 
-  compiler = fetchNimble {
-    pname = "compiler";
-    version = "1.4.8";
-    hash = "sha256-OaSe9Bn/+rjVk4pJKjjwI9rpnDm/T7lRmKeh/DOPn38=";
-  };
-
-  npeg = fetchNimble {
-    pname = "npeg";
-    version = "0.24.1";
-    hash = "sha256-AKYDrR38345CQxV7kLvglGmkc/m8EX6TGtaFckJL3Dc=";
+  npeg = fetchFromGitHub {
+    owner = "zevv";
+    repo = "npeg";
+    rev = "0.25.0";
+    hash = "sha256-E/0hCz0XsoAb/bAksqrKTyi8/FwBdP8kT6uUUAdru68=";
   };
 
 in buildNimPackage rec {
   outputs = [ "out" "dev" ];
 
   pname = "preserves";
-  version = "2.0.0";
+  version = "3.0.0";
   src = fetchFromGitea {
     domain = "git.syndicate-lang.org";
     owner = "ehmry";
     repo = "preserves-nim";
     rev = "v${version}";
-    sha256 = "sha256-DRncKqq9+2WR1V1EeTnAh7ObCUNqfz7hp8onrCi1mlA=";
+    sha256 = "sha256-YcWJkDJIo1UcXyqQTv82ebDeT03f5LqnuIKVtkvBClA=";
   };
-  buildInputs = [ compiler bigints npeg ];
+  buildInputs = [ compiler npeg ];
   postInstall = ''
     pushd $out/bin
     for link in preserves_decode preserves_from_json preserves_to_json;