diff --git a/src/blockstore/blockstore_flush.cpp b/src/blockstore/blockstore_flush.cpp
index 9e89bd1c..cc91a43a 100644
--- a/src/blockstore/blockstore_flush.cpp
+++ b/src/blockstore/blockstore_flush.cpp
@@ -409,7 +409,10 @@ int journal_flusher_co::check_and_punch_checksums()
         auto & vec = read_vec[i];
         if (!(vec.copy_flags & (COPY_BUF_COALESCED|COPY_BUF_ZERO)))
         {
-            heap_write_t *wr = (heap_write_t*)((uint8_t*)cur_obj + vec.wr_offset);
+            heap_write_t *wr = cur_obj->get_writes();
+            while (wr && wr->lsn != vec.wr_lsn)
+                wr = wr->next();
+            assert(wr);
             bs->heap->calc_block_checksums(
                 (uint32_t*)wr->get_checksums(bs->heap), vec.buf, wr->get_int_bitmap(bs->heap), vec.offset, vec.offset+vec.len, false,
                 [&](uint32_t mismatch_pos, uint32_t expected_csum, uint32_t real_csum)
@@ -434,7 +437,7 @@ int journal_flusher_co::check_and_punch_checksums()
         // Nothing to do
         return 0;
     }
-    cur_obj = bs->heap->read_entry(cur_oid, &modified_block);
+    cur_obj = bs->heap->read_entry(cur_oid, &modified_block, true);
     if (!cur_obj)
     {
         // Object is deleted, abort compaction
@@ -498,10 +501,13 @@ void journal_flusher_co::calc_block_checksums()
         auto len = it->len;
         while ((block_done+len) >= bs->dsk.csum_block_size)
         {
-            if (!block_done && it->wr_offset)
+            if (!block_done && it->wr_lsn)
             {
                 // We may take existing checksums if an overwrite contains a full block
-                heap_write_t *wr = (heap_write_t*)((uint8_t*)cur_obj + it->wr_offset);
+                heap_write_t *wr = cur_obj->get_writes();
+                while (wr && wr->lsn != it->wr_lsn)
+                    wr = wr->next();
+                assert(wr);
                 assert(!(it->offset % bs->dsk.csum_block_size));
                 assert(!(wr->offset % bs->dsk.csum_block_size));
                 auto full_csum_offset = (it->offset - wr->offset) / bs->dsk.csum_block_size;
diff --git a/src/blockstore/blockstore_flush.h b/src/blockstore/blockstore_flush.h
index 69cac4f1..4b18a99a 100644
--- a/src/blockstore/blockstore_flush.h
+++ b/src/blockstore/blockstore_flush.h
@@ -6,7 +6,7 @@ struct copy_buffer_t
     int copy_flags;
     uint64_t offset, len, disk_offset, disk_len;
     uint8_t *buf;
-    uint32_t wr_offset;
+    uint64_t wr_lsn;
 };
 
 struct meta_sector_t
diff --git a/src/blockstore/blockstore_read.cpp b/src/blockstore/blockstore_read.cpp
index aa363fad..7f84ee37 100644
--- a/src/blockstore/blockstore_read.cpp
+++ b/src/blockstore/blockstore_read.cpp
@@ -194,7 +194,7 @@ uint32_t blockstore_impl_t::prepare_read_simple(std::vector<copy_buffer_t> & rea
                 .disk_offset = wr->location + start - wr->offset,
                 .disk_len = end-start,
                 .buf = buffer_area + wr->location + start - wr->offset,
-                .wr_offset = (uint32_t)((uint8_t*)wr - (uint8_t*)obj),
+                .wr_lsn = wr->lsn,
             });
         }
         else if (dsk.csum_block_size <= dsk.bitmap_granularity)
@@ -243,7 +243,7 @@ void blockstore_impl_t::prepare_disk_read(std::vector<copy_buffer_t> & read_vec,
         .len = end-start,
         .disk_offset = wr->location + blk_start - wr->offset,
         .disk_len = blk_end - blk_start,
-        .wr_offset = (uint32_t)((uint8_t*)wr - (uint8_t*)obj),
+        .wr_lsn = wr->lsn,
     };
     if (blk_start != start || blk_end != end)
     {
@@ -330,7 +330,10 @@ bool blockstore_impl_t::verify_read_checksums(blockstore_op_t *op)
         {
             continue;
         }
-        heap_write_t *wr = (heap_write_t*)((uint8_t*)obj + vec.wr_offset);
+        heap_write_t *wr = obj->get_writes();
+        while (wr && wr->lsn != vec.wr_lsn)
+            wr = wr->next();
+        assert(wr);
         uint32_t blk_start = vec.offset, blk_end = vec.offset + vec.len;
         if (vec.copy_flags & COPY_BUF_PADDED)
         {