diff --git a/modules/autoupdate.nix b/modules/autoupdate.nix
index e677265e..e474508e 100644
--- a/modules/autoupdate.nix
+++ b/modules/autoupdate.nix
@@ -59,6 +59,7 @@
     nix.gc = lib.mkIf config.c3d2.autoUpdate {
       automatic = true;
       randomizedDelaySec = "6h";
+      options = "--delete-older-than 21d"
     };
 
     # Always show a diff when activating a new system