diff --git a/pkgs/servers/klipper/default.nix b/pkgs/servers/klipper/default.nix
index 490bb9c9e094..7b2bb8d4df95 100644
--- a/pkgs/servers/klipper/default.nix
+++ b/pkgs/servers/klipper/default.nix
@@ -23,7 +23,7 @@ stdenv.mkDerivation rec {
   # NB: This is needed for the postBuild step
   nativeBuildInputs = [ (python2.withPackages ( p: with p; [ cffi ] )) ];
 
-  buildInputs = [ (python2.withPackages (p: with p; [ cffi pyserial greenlet jinja2 ])) ];
+  buildInputs = [ (python2.withPackages (p: with p; [ cffi pyserial greenlet jinja2 numpy ])) ];
 
   # we need to run this to prebuild the chelper.
   postBuild = "python2 ./chelper/__init__.py";