diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c
index d107d76..d354dc2 100644
--- a/src/backend/optimizer/path/costsize.c
+++ b/src/backend/optimizer/path/costsize.c
@@ -516,7 +516,12 @@ cost_index(IndexPath *path, PlannerInfo *root, double loop_count)
 	cost_qual_eval(&qpqual_cost, qpquals, root);
 
 	startup_cost += qpqual_cost.startup;
-	cpu_per_tuple = cpu_tuple_cost + qpqual_cost.per_tuple;
+
+	/* Indexonly scan applies this qual on index tuples */
+	if (indexonly)
+		cpu_per_tuple = cpu_index_tuple_cost + qpqual_cost.per_tuple;
+	else
+		cpu_per_tuple = cpu_tuple_cost + qpqual_cost.per_tuple;
 
 	run_cost += cpu_per_tuple * tuples_fetched;