diff --git a/src/buffer.hh b/src/buffer.hh
index 7402f769..a5e3e5ae 100644
--- a/src/buffer.hh
+++ b/src/buffer.hh
@@ -198,7 +198,6 @@ private:
 
     struct Modification;
     using  UndoGroup = Vector<Modification, MemoryDomain::BufferMeta>;
-    friend class UndoGroupOptimizer;
 
     using History = Vector<UndoGroup, MemoryDomain::BufferMeta>;
     History           m_history;