diff --git a/pkgs/development/python-modules/kaldi-active-grammar/default.nix b/pkgs/development/python-modules/kaldi-active-grammar/default.nix
index 192e48ab78f1..38c00df1b2db 100644
--- a/pkgs/development/python-modules/kaldi-active-grammar/default.nix
+++ b/pkgs/development/python-modules/kaldi-active-grammar/default.nix
@@ -34,8 +34,10 @@ buildPythonPackage rec {
     sha256 = "sha256-VyVshIEVp/ep4Ih7Kj66GF02JEZ4nwgJOtgR2DarzdY=";
   };
 
-  KALDI_BRANCH = "foo";
-  KALDIAG_SETUP_RAW = "1";
+  env = {
+    KALDI_BRANCH = "foo";
+    KALDIAG_SETUP_RAW = "1";
+  };
 
   patches = [
     # Makes sure scikit-build doesn't try to build the dependencies for us