diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c
index 7bf67a05295..db9d62844b1 100644
--- a/src/backend/optimizer/path/costsize.c
+++ b/src/backend/optimizer/path/costsize.c
@@ -272,6 +272,7 @@ cost_seqscan(Path *path, PlannerInfo *root,
 	}
 
 	path->startup_cost = startup_cost;
+	path->startup_cost += (cpu_run_cost + disk_run_cost) / (2.0 * path->rows);
 	path->total_cost = startup_cost + cpu_run_cost + disk_run_cost;
 }