diff --git a/flake.nix b/flake.nix
index e0e06255..ba7b38df 100644
--- a/flake.nix
+++ b/flake.nix
@@ -96,6 +96,10 @@
       inherit (nixpkgs) lib;
       forAllSystems = lib.genAttrs [ "aarch64-linux" "x86_64-linux" ];
 
+      # all the input flakes for `nix copy` to the build machine,
+      # allowing --override-input
+      inputPaths = lib.escapeShellArgs (builtins.attrValues inputs);
+
       extractZwHosts = { hosts4, hosts6, ... }:
         lib.recursiveUpdate (
           builtins.foldl' (result: name:
@@ -195,8 +199,7 @@
           prebuild-all-remote = pkgs.writeScriptBin "prebuild-all" ''
             #!${pkgs.runtimeShell} -e
 
-            nix copy --to ssh://$1 ${secrets}
-            nix copy --to ssh://$1 ${self}
+            nix copy --to ssh://$1 ${inputPaths}
 
             set -x
             ssh $1 -- nix build -L --no-link ${
@@ -234,17 +237,14 @@
             "${name}-nixos-rebuild" = pkgs.writeScriptBin "${name}-nixos-rebuild" ''
               #!${pkgs.runtimeShell} -ex
               [[ $(ssh ${target} cat /etc/hostname) == ${name} ]]
-              nix copy --to ssh://${target} ${secrets}
-              nix copy --to ssh://${target} ${self}
+              nix copy --to ssh://${target} ${inputPaths}
               ssh ${target} nixos-rebuild ${rebuildArg} "$@"
             '';
 
             "${name}-nixos-rebuild-hydra" = pkgs.writeScriptBin "${name}-nixos-rebuild" ''
               #!${pkgs.runtimeShell} -e
-              echo Copying Flakes 1/2
-              nix copy --to ssh://root@hydra.serv.zentralwerk.org ${secrets}
-              echo Copying Flakes 2/2
-              nix copy --to ssh://root@hydra.serv.zentralwerk.org ${self}
+              echo Copying Flakes
+              nix copy --to ssh://root@hydra.serv.zentralwerk.org ${inputPaths}
               echo Building on Hydra
               ssh root@hydra.serv.zentralwerk.org -- \
                 nix build -L -o /tmp/nixos-system-${name} \
@@ -277,7 +277,7 @@
           } // lib.optionalAttrs (builtins.elem (hostConfig.c3d2.deployment.server or null) [ "server9" "server10" ]) {
             "microvm-update-${name}" = pkgs.writeScriptBin "microvm-update-${name}" ''
               #!${pkgs.runtimeShell} -e
-              ${hostConfig.system.build.copyToServer} ${self} ${secrets}
+              ${hostConfig.system.build.copyToServer} ${inputPaths}
 
               ${hostConfig.system.build.runOnServer} bash -e <<END
               mkdir -p /var/lib/microvms/${name}