diff --git a/modules/nix-common/default.nix b/modules/nix-common/default.nix
index 439cd3e..9842cfb 100644
--- a/modules/nix-common/default.nix
+++ b/modules/nix-common/default.nix
@@ -66,7 +66,7 @@ in
       gc = {
         automatic = true;
         dates = "daily";
-        options = "--delete-older-than=30d";
+        options = "--delete-older-than 30d";
       };
     };