diff --git a/nixos-modules/hydra.nix b/nixos-modules/hydra.nix
index 97906cb34..1ea845f32 100644
--- a/nixos-modules/hydra.nix
+++ b/nixos-modules/hydra.nix
@@ -467,7 +467,7 @@ in
             if [[ $compression == zstd ]]; then
               compression="zstd --rm"
             fi
-            find ${baseDir}/build-logs -type f -name "*.drv" -mtime +3 -size +0c | xargs -r $compression --force --quiet
+            find ${baseDir}/build-logs -type f -name "*.drv" -mtime +3 -size +0c | xargs -r ''${compression:-bzip2} --force --quiet
           '';
         startAt = "Sun 01:45";
       };