diff --git a/nixos/modules/virtualisation/qemu-vm.nix b/nixos/modules/virtualisation/qemu-vm.nix
index 69d67685f559..c5f71b249a6d 100644
--- a/nixos/modules/virtualisation/qemu-vm.nix
+++ b/nixos/modules/virtualisation/qemu-vm.nix
@@ -780,7 +780,7 @@ in
       in
       [
         "-net nic,netdev=user.0,model=virtio"
-        "-netdev user,id=user.0,${forwardingOptions}\${QEMU_NET_OPTS:+,$QEMU_NET_OPTS}"
+        "-netdev user,id=user.0,${forwardingOptions}\"$QEMU_NET_OPTS\""
       ];
 
     # FIXME: Consolidate this one day.