diff --git a/derivations.nix b/derivations.nix
index f8519e6..7f2a3d8 100644
--- a/derivations.nix
+++ b/derivations.nix
@@ -16,18 +16,5 @@ rec {
   heavycomps = pkgs.callPackage ./heavycomps.nix { inherit nmigen; };
 
   binutils-riscv = pkgs.callPackage ./compilers/binutils.nix { platform = "riscv32"; };
-  llvm_7 = pkgs.llvm_7.overrideAttrs(oa: {
-    name = oa.name + "-riscv";
-    cmakeFlags = oa.cmakeFlags ++ ["-DLLVM_EXPERIMENTAL_TARGETS_TO_BUILD=RISCV"];
-  });
-  rustc = (pkgs.rustc.overrideAttrs(oa: {
-    name = "${oa.pname}-${oa.version}-riscv";
-  })).override {
-    inherit llvm_7;
-    pkgsBuildBuild = pkgs.pkgsBuildBuild // { inherit llvm_7; };
-    pkgsBuildHost = pkgs.pkgsBuildHost // { inherit llvm_7; };
-    pkgsBuildTarget = pkgs.pkgsBuildTarget // { inherit llvm_7; };
-  };
-  rust-riscv32imc-crates = pkgs.callPackage ./compilers/rust-riscv32imc-crates.nix { inherit rustc; };
-  cargo = pkgs.cargo.override { inherit rustc; };
+  rust-riscv32imc-crates = pkgs.callPackage ./compilers/rust-riscv32imc-crates.nix { };
 }
diff --git a/overlay.nix b/overlay.nix
new file mode 100644
index 0000000..1a0624b
--- /dev/null
+++ b/overlay.nix
@@ -0,0 +1,7 @@
+self: super:
+{
+  llvm_7 = super.llvm_7.overrideAttrs(oa: {
+    name = oa.name + "-riscv";
+    cmakeFlags = oa.cmakeFlags ++ ["-DLLVM_EXPERIMENTAL_TARGETS_TO_BUILD=RISCV"];
+  });
+}
diff --git a/release.nix b/release.nix
index 90ee405..0ca1ce7 100644
--- a/release.nix
+++ b/release.nix
@@ -1,7 +1,12 @@
-{ pkgs ? import <nixpkgs> {}}:
+{ }:
 let
+  pkgs = import <nixpkgs> { overlays = [ import ./overlay.nix ]; };
   derivations = import ./derivations.nix { inherit pkgs; };
   jobs = derivations // {
+    rustc = pkgs.rustc;
+    cargo = pkgs.cargo;
+    cargo-vendor = pkgs.cargo-vendor;
+
     helloworld_ecp5 = import ./examples/helloworld_ecp5.nix { inherit pkgs; };
     helloworld_kintex7 = import ./examples/helloworld_kintex7.nix { inherit pkgs; };
     simplesoc_ecp5 = import ./examples/simplesoc_ecp5.nix { inherit pkgs; };
diff --git a/shell-firmware.nix b/shell-firmware.nix
index be9a9b5..3743033 100644
--- a/shell-firmware.nix
+++ b/shell-firmware.nix
@@ -1,5 +1,6 @@
-{ pkgs ? import <nixpkgs> {}}:
+{ }:
 let
+  pkgs = import <nixpkgs> { overlays = [ import ./overlay.nix ]; };
   hx = import ./derivations.nix { inherit pkgs; };
 in
   pkgs.mkShell {