diff --git a/pkgs/applications/science/math/polymake/default.nix b/pkgs/applications/science/math/polymake/default.nix
index fdc4de7b028..d4f13f84f81 100644
--- a/pkgs/applications/science/math/polymake/default.nix
+++ b/pkgs/applications/science/math/polymake/default.nix
@@ -28,7 +28,7 @@ stdenv.mkDerivation rec {
     makeWrapper ninja ant perl
   ];
 
-  ninjaFlags = "-C build/Opt";
+  ninjaFlags = [ "-C" "build/Opt" ];
 
   postInstall = ''
     for i in "$out"/bin/*; do