diff --git a/common/global/default.nix b/common/global/default.nix
index e9f8766..9768aca 100644
--- a/common/global/default.nix
+++ b/common/global/default.nix
@@ -32,6 +32,7 @@
     useGlobalPkgs = true;
     useUserPackages = true;
     extraSpecialArgs = {inherit inputs outputs;};
+    backupFileExtension = "backup";
   };
 
   nixpkgs = {