diff --git a/nixos-modules/hydra.nix b/nixos-modules/hydra.nix
index 97906cb34..d001675da 100644
--- a/nixos-modules/hydra.nix
+++ b/nixos-modules/hydra.nix
@@ -464,10 +464,12 @@ in
           ''
             set -eou pipefail
             compression=$(sed -nr 's/compress_build_logs_compression = ()/\1/p' ${baseDir}/hydra.conf)
-            if [[ $compression == zstd ]]; then
+            if [[ $compression == "" ]]; then
+              compression="bzip2"
+            elif [[ $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" --force --quiet
           '';
         startAt = "Sun 01:45";
       };