diff --git a/nix/windows/default.nix b/nix/windows/default.nix
index d4e787d1..f41a3e9b 100644
--- a/nix/windows/default.nix
+++ b/nix/windows/default.nix
@@ -69,7 +69,7 @@ in rec {
       '';
     buildPhase =
       ''
-      wine64 ninja
+      wine64 ninja -j $NIX_BUILD_CORES
       '';
     installPhase =
       ''