diff --git a/src/libstore/local-store.hh b/src/libstore/local-store.hh
index f1e2ab7f9..5e07261a6 100644
--- a/src/libstore/local-store.hh
+++ b/src/libstore/local-store.hh
@@ -90,6 +90,8 @@ private:
         std::unique_ptr<PublicKeys> publicKeys;
     };
 
+    // FIXME: get rid of recursive_mutex, it hides recursive SQLite
+    // queries.
     Sync<State, std::recursive_mutex> _state;
 
 public: