diff --git a/artiq/artiq-board.nix b/artiq/artiq-board.nix
index dfbbe1e..d2ff017 100644
--- a/artiq/artiq-board.nix
+++ b/artiq/artiq-board.nix
@@ -1,7 +1,7 @@
 # Install Vivado in /opt and add to /etc/nixos/configuration.nix:
 #  nix.sandboxPaths = ["/opt"];
 
-{ pkgs ? import <nixpkgs> {}}:
+{ pkgs }:
 { target
 , variant
 , buildCommand ? "python -m artiq.gateware.targets.${target} -V ${variant}"
diff --git a/artiq/windows/run-test.nix b/artiq/windows/run-test.nix
index d9a7935..dc15b43 100644
--- a/artiq/windows/run-test.nix
+++ b/artiq/windows/run-test.nix
@@ -1,4 +1,4 @@
-{ pkgs ? import <nixpkgs> {},
+{ pkgs,
   diskImage ? "/opt/windows/c.img",
   qemuMem ? "2G",
   testTimeout ? 600,