diff --git a/pkgs/by-name/ba/bant/package.nix b/pkgs/by-name/ba/bant/package.nix
index 6b364c284223..fbf07613ed3c 100644
--- a/pkgs/by-name/ba/bant/package.nix
+++ b/pkgs/by-name/ba/bant/package.nix
@@ -33,7 +33,10 @@ buildBazelPackage rec {
     "--registry"
     "file://${registry}"
   ];
-  LIBTOOL = lib.optionalString stdenv.hostPlatform.isDarwin "${cctools}/bin/libtool";
+
+  env = lib.optionalAttrs stdenv.hostPlatform.isDarwin {
+    LIBTOOL = "${cctools}/bin/libtool";
+  };
 
   postPatch = ''
     patchShebangs scripts/create-workspace-status.sh