diff --git a/nixos/hosts/sunken-ship.nix b/nixos/hosts/sunken-ship.nix
index ad78f70..768a0df 100644
--- a/nixos/hosts/sunken-ship.nix
+++ b/nixos/hosts/sunken-ship.nix
@@ -321,6 +321,8 @@
       fastapi
       uvicorn
       python-multipart
+      mutagen   # tag writeback (enrich.write_tags); needed by the
+                # /enrich/revert endpoint which reuses enrich.py.
     ]);
   in {
     description = "Mulbo companion service (uploads, dedup, folders)";