diff --git a/nixos/modules/virtualisation/virtualbox-image.nix b/nixos/modules/virtualisation/virtualbox-image.nix
index 840ac2e291d6..ab65523592d7 100644
--- a/nixos/modules/virtualisation/virtualbox-image.nix
+++ b/nixos/modules/virtualisation/virtualbox-image.nix
@@ -100,10 +100,10 @@ in {
     boot.growPartition = true;
     boot.loader.grub.device = "/dev/sda";
 
-    swap.swapDevices = {
+    swapDevices = [{
       device = "/var/swap";
       size = 2048;
-    };
+    }];
 
     virtualisation.virtualbox.guest.enable = true;