diff --git a/pkgs/by-name/pk/pkl/package.nix b/pkgs/by-name/pk/pkl/package.nix
index af961ce14aef..60cfea9cc871 100644
--- a/pkgs/by-name/pk/pkl/package.nix
+++ b/pkgs/by-name/pk/pkl/package.nix
@@ -67,7 +67,7 @@ stdenv.mkDerivation (finalAttrs: {
     gradleFlagsArray+=(-DcommitId=$(cat .commit-hash))
   '';
 
-  JAVA_TOOL_OPTIONS = "-Dfile.encoding=utf-8";
+  env.JAVA_TOOL_OPTIONS = "-Dfile.encoding=utf-8";
   __darwinAllowLocalNetworking = true;
 
   preCheck = ''