diff --git a/pkgs/applications/virtualization/qemu/default.nix b/pkgs/applications/virtualization/qemu/default.nix
index c04d3b33945..a3f737e4a81 100644
--- a/pkgs/applications/virtualization/qemu/default.nix
+++ b/pkgs/applications/virtualization/qemu/default.nix
@@ -177,6 +177,9 @@ stdenv.mkDerivation rec {
     qemu-system-i386 = "bin/qemu-system-i386";
   };
 
+  # Builds in ~3h with 2 cores, and ~20m with a big-parallel builder.
+  requiredSystemFeatures = [ "big-parallel" ];
+
   meta = with lib; {
     homepage = "http://www.qemu.org/";
     description = "A generic and open source machine emulator and virtualizer";