diff --git a/pkgs/by-name/op/openzwave/package.nix b/pkgs/by-name/op/openzwave/package.nix
index 1d27e9bf8640..a593b6c93ed4 100644
--- a/pkgs/by-name/op/openzwave/package.nix
+++ b/pkgs/by-name/op/openzwave/package.nix
@@ -46,8 +46,10 @@ stdenv.mkDerivation {
     "PREFIX=${placeholder "out"}"
   ];
 
-  FONTCONFIG_FILE = "${fontconfig.out}/etc/fonts/fonts.conf";
-  FONTCONFIG_PATH = "${fontconfig.out}/etc/fonts/";
+  env = {
+    FONTCONFIG_FILE = "${fontconfig.out}/etc/fonts/fonts.conf";
+    FONTCONFIG_PATH = "${fontconfig.out}/etc/fonts/";
+  };
 
   postPatch = ''
     substituteInPlace cpp/src/Options.cpp \