diff --git a/pkgs/by-name/ki/kicad/libraries.nix b/pkgs/by-name/ki/kicad/libraries.nix
index 5a4504e1120d..9dd439801019 100644
--- a/pkgs/by-name/ki/kicad/libraries.nix
+++ b/pkgs/by-name/ki/kicad/libraries.nix
@@ -28,7 +28,7 @@ let
 
       postInstall =
         lib.optionalString (name == "packages3d") ''
-          find $out -type f -name '*.step' | parallel 'stepreduce {} {} ${lib.optionalString compressStep "&& zip -9 {.}.stpZ {} && rm {}"}'
+          find $out -type f -name '*.step' | parallel 'stepreduce {} {} ${lib.optionalString compressStep "&& zip -j -9 {.}.stpZ {} && rm {}"}'
         ''
         + lib.optionalString ((name == "footprints") && compressStep) ''
           grep -rl '\.step' $out | xargs sed -i 's/\.step/.stpZ/g'