diff --git a/pkgs/by-name/gn/gnome-network-displays/package.nix b/pkgs/by-name/gn/gnome-network-displays/package.nix
index b10568e8d94b..9e3ec5c16c23 100644
--- a/pkgs/by-name/gn/gnome-network-displays/package.nix
+++ b/pkgs/by-name/gn/gnome-network-displays/package.nix
@@ -78,7 +78,7 @@ stdenv.mkDerivation (finalAttrs: {
     Hence, this is not necessarily an upstream issue, but could be something
     wrong with how our gst_all_1 depend on each other.
   */
-  CFLAGS = "-I${gst_all_1.gst-plugins-base.dev}/include/gstreamer-1.0";
+  env.CFLAGS = "-I${gst_all_1.gst-plugins-base.dev}/include/gstreamer-1.0";
 
   preConfigure = ''
     patchShebangs ./build-aux/meson/postinstall.py