diff --git a/pageserver/src/walredo.rs b/pageserver/src/walredo.rs
index 6918698f29..3bec2846e9 100644
--- a/pageserver/src/walredo.rs
+++ b/pageserver/src/walredo.rs
@@ -414,7 +414,7 @@ impl PostgresRedoManager {
                     "ClearVisibilityMapFlags record on unexpected rel {}",
                     rel
                 );
-                if let Some(heap_blkno) = *new_heap_blkno {
+                let mut doit = |heap_blkno| {
                     // Calculate the VM block and offset that corresponds to the heap block.
                     let map_block = pg_constants::HEAPBLK_TO_MAPBLOCK(heap_blkno);
                     let map_byte = pg_constants::HEAPBLK_TO_MAPBYTE(heap_blkno);
@@ -427,19 +427,12 @@ impl PostgresRedoManager {
                     let map = &mut page[pg_constants::MAXALIGN_SIZE_OF_PAGE_HEADER_DATA..];
 
                     map[map_byte as usize] &= !(flags << map_offset);
+                };
+                if let Some(heap_blkno) = *new_heap_blkno {
+                    doit(heap_blkno);
                 }
-
-                // Repeat for 'old_heap_blkno', if any
                 if let Some(heap_blkno) = *old_heap_blkno {
-                    let map_block = pg_constants::HEAPBLK_TO_MAPBLOCK(heap_blkno);
-                    let map_byte = pg_constants::HEAPBLK_TO_MAPBYTE(heap_blkno);
-                    let map_offset = pg_constants::HEAPBLK_TO_OFFSET(heap_blkno);
-
-                    assert!(map_block == blknum);
-
-                    let map = &mut page[pg_constants::MAXALIGN_SIZE_OF_PAGE_HEADER_DATA..];
-
-                    map[map_byte as usize] &= !(flags << map_offset);
+                    doit(heap_blkno);
                 }
             }
             // Non-relational WAL records are handled here, with custom code that has the