diff --git a/modules/programs/virtualbox.nix b/modules/programs/virtualbox.nix
index 60f58c922b9..cb293563dfd 100644
--- a/modules/programs/virtualbox.nix
+++ b/modules/programs/virtualbox.nix
@@ -31,5 +31,5 @@ let virtualbox = config.boot.kernelPackages.virtualbox; in
         '';
     };
 
-  networking.interfaces = [ { name = "vboxnet0"; ipAddress = "192.168.56.1"; } ];
+  networking.interfaces = [ { name = "vboxnet0"; ipAddress = "192.168.56.1"; subnetMask = "255.255.255.0"; } ];
 }