diff --git a/.gitignore b/.gitignore
index f716139..1ef70e3 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,2 @@
-/.direnv
-*.html
-*.run
+/nim.cfg
+/tests/*.run
diff --git a/Tupfile b/Tupfile
new file mode 100644
index 0000000..28c450e
--- /dev/null
+++ b/Tupfile
@@ -0,0 +1,2 @@
+include_rules
+: lock.json |> !nim_cfg |> | ./<lock>
diff --git a/Tuprules.tup b/Tuprules.tup
index 335dbc7..5eb62bf 100644
--- a/Tuprules.tup
+++ b/Tuprules.tup
@@ -1 +1,2 @@
 include depends.tup
+NIM_GROUPS += $(TUP_CWD)/<lock>
diff --git a/depends.tup b/depends.tup
index 9134156..8058986 100644
--- a/depends.tup
+++ b/depends.tup
@@ -1,2 +1 @@
 NIM_FLAGS += --path:$(TUP_CWD)/../nim
-NIM_FLAGS += --path:$(TUP_CWD)/../nimble/npeg/src
diff --git a/lock.json b/lock.json
new file mode 100644
index 0000000..046a779
--- /dev/null
+++ b/lock.json
@@ -0,0 +1 @@
+{"depends":[{"method":"fetchzip","packages":["npeg"],"path":"/nix/store/ffkxmjmigfs7zhhiiqm0iw2c34smyciy-source","ref":"1.2.1","rev":"26d62fdc40feb84c6533956dc11d5ee9ea9b6c09","sha256":"0xpzifjkfp49w76qmaylan8q181bs45anmp46l4bwr3lkrr7bpwh","srcDir":"src","url":"https://github.com/zevv/npeg/archive/26d62fdc40feb84c6533956dc11d5ee9ea9b6c09.tar.gz"}]}
diff --git a/preserves.nimble b/preserves.nimble
index 4aea90c..b576b1c 100644
--- a/preserves.nimble
+++ b/preserves.nimble
@@ -11,4 +11,4 @@ bin           = @["preserves/preserves_schema_nim", "preserves/private/preserves
 
 # Dependencies
 
-requires "nim >= 2.0.0", "compiler >= 1.4.8", "npeg"
+requires "nim >= 2.0.0", "compiler >= 1.4.8", "https://github.com/zevv/npeg.git >= 1.2.1"
diff --git a/shell.nix b/shell.nix
index 507597d..24f8937 100644
--- a/shell.nix
+++ b/shell.nix
@@ -1,5 +1,2 @@
-let
-  syndicate = builtins.getFlake "syndicate";
-  pkgs =
-    import <nixpkgs> { overlays = builtins.attrValues syndicate.overlays; };
-in pkgs.nim2Packages.preserves
+{ pkgs ? import <nixpkgs> { } }:
+pkgs.nim2Packages.buildNimPackage { name = "dummy"; }