diff --git a/src/backend/optimizer/util/plancat.c b/src/backend/optimizer/util/plancat.c
index 265c865fcb..fb7db6d959 100644
--- a/src/backend/optimizer/util/plancat.c
+++ b/src/backend/optimizer/util/plancat.c
@@ -509,7 +509,7 @@ estimate_rel_size(Relation rel, int32 *attr_widths,
 
 				tuple_width = get_rel_data_width(rel, attr_widths);
 				tuple_width += sizeof(HeapTupleHeaderData);
-				tuple_width += sizeof(ItemPointerData);
+				tuple_width += sizeof(ItemIdData);
 				/* note: integer division is intentional here */
 				density = (BLCKSZ - SizeOfPageHeaderData) / tuple_width;
 			}