diff --git a/flake.nix b/flake.nix
index b434767c..ed64ef9b 100644
--- a/flake.nix
+++ b/flake.nix
@@ -253,10 +253,17 @@
               cd /var/lib/microvms/${name}
               chown root:kvm .
               chmod 0775 .
+
+              rm -f old
+              [ -e current ] && mv current old
+
               nix build -L \
                 -o current \
                 ${self}#nixosConfigurations.${name}.config.microvm.declaredRunner
               echo '${selfRef}' > flake
+
+              [ -e old ] && nix store diff-closures ./old ./current
+
               systemctl restart microvm@${name}.service
               END
             '';
@@ -270,9 +277,15 @@
               cd /var/lib/microvms/${name}
               chown root:kvm .
               chmod 0775 .
-              rm -f current
+
+              rm -f old
+              [ -e current ] && mv current old
+
               ln -s ${hostConfig.microvm.declaredRunner} current
               echo '${selfRef}' > flake
+
+              [ -e old ] && nix store diff-closures ./old ./current
+
               systemctl restart microvm@${name}.service
               END
             '';