diff --git a/pkgs/by-name/th/thc-hydra/package.nix b/pkgs/by-name/th/thc-hydra/package.nix
index b27d967fabb5..db87bf2d2597 100644
--- a/pkgs/by-name/th/thc-hydra/package.nix
+++ b/pkgs/by-name/th/thc-hydra/package.nix
@@ -63,7 +63,7 @@ stdenv.mkDerivation rec {
 
   enableParallelBuilding = true;
 
-  DATADIR = "/share/${pname}";
+  env.DATADIR = "/share/${pname}";
 
   postInstall = lib.optionalString withGUI ''
     wrapProgram $out/bin/xhydra \