diff --git a/pkgs/by-name/qb/qbootctl/package.nix b/pkgs/by-name/qb/qbootctl/package.nix
index d7f8607fb5c0..aace7b25fe1a 100644
--- a/pkgs/by-name/qb/qbootctl/package.nix
+++ b/pkgs/by-name/qb/qbootctl/package.nix
@@ -25,7 +25,7 @@ stdenv.mkDerivation (finalAttrs: {
     linuxHeaders
   ];
 
-  CFLAGS = [ "-I${linuxHeaders}/include" ];
+  env.CFLAGS = toString [ "-I${linuxHeaders}/include" ];
 
   passthru.updateScript = nix-update-script { };