diff a/src/hotspot/share/gc/z/zLiveMap.hpp b/src/hotspot/share/gc/z/zLiveMap.hpp
--- a/src/hotspot/share/gc/z/zLiveMap.hpp
+++ b/src/hotspot/share/gc/z/zLiveMap.hpp
@@ -43,10 +43,11 @@
   const int         _segment_shift;
 
   Atomic<uint32_t>  _seqnum;
   Atomic<uint32_t>  _live_objects;
   Atomic<size_t>    _live_bytes;
+  Atomic<uint32_t>  _will_expand_objects;
   BitMap::bm_word_t _segment_live_bits;
   BitMap::bm_word_t _segment_claim_bits;
   ZBitMap           _bitmap;
 
   const BitMapView segment_live_bits() const;
@@ -85,15 +86,17 @@
 
   bool is_marked(ZGenerationId id) const;
 
   uint32_t live_objects() const;
   size_t live_bytes() const;
+  uint32_t will_expand_objects() const;
 
   bool get(ZGenerationId id, BitMap::idx_t index) const;
   bool set(ZGenerationId id, BitMap::idx_t index, bool finalizable, bool& inc_live);
 
   void inc_live(uint32_t objects, size_t bytes);
+  void inc_will_expand(uint32_t objects);
 
   template <typename Function>
   void iterate(ZGenerationId id, Function function);
 
   BitMap::idx_t find_base_bit(BitMap::idx_t index);