diff --git a/pkgs/by-name/mu/mutter/package.nix b/pkgs/by-name/mu/mutter/package.nix
index 4653bb2c718d..7e4936322523 100644
--- a/pkgs/by-name/mu/mutter/package.nix
+++ b/pkgs/by-name/mu/mutter/package.nix
@@ -198,7 +198,7 @@ stdenv.mkDerivation (finalAttrs: {
   '';
 
   # Install udev files into our own tree.
-  PKG_CONFIG_UDEV_UDEVDIR = "${placeholder "out"}/lib/udev";
+  env.PKG_CONFIG_UDEV_UDEVDIR = "${placeholder "out"}/lib/udev";
 
   separateDebugInfo = true;
   strictDeps = true;
diff --git a/pkgs/by-name/mu/mutter46/package.nix b/pkgs/by-name/mu/mutter46/package.nix
index f215ef9fd523..c2045eeb3060 100644
--- a/pkgs/by-name/mu/mutter46/package.nix
+++ b/pkgs/by-name/mu/mutter46/package.nix
@@ -184,7 +184,7 @@ stdenv.mkDerivation (finalAttrs: {
   '';
 
   # Install udev files into our own tree.
-  PKG_CONFIG_UDEV_UDEVDIR = "${placeholder "out"}/lib/udev";
+  env.PKG_CONFIG_UDEV_UDEVDIR = "${placeholder "out"}/lib/udev";
 
   separateDebugInfo = true;