diff --git a/src/backend/optimizer/util/plancat.c b/src/backend/optimizer/util/plancat.c
index e553afb7f01..bf45c355b77 100644
--- a/src/backend/optimizer/util/plancat.c
+++ b/src/backend/optimizer/util/plancat.c
@@ -999,6 +999,15 @@ infer_arbiter_indexes(PlannerInfo *root)
 		if (!idxForm->indisready)
 			continue;
 
+		/*
+		 * Ignore invalid indexes for partitioned tables.  It's possible that
+		 * some partitions don't have the index (yet), and then we would not
+		 * find a match during ExecInitPartitionInfo.
+		 */
+		if (relation->rd_rel->relkind == RELKIND_PARTITIONED_TABLE &&
+			!idxForm->indisvalid)
+			continue;
+
 		/*
 		 * Note that we do not perform a check against indcheckxmin (like e.g.
 		 * get_relation_info()) here to eliminate candidates, because
diff --git a/src/test/regress/expected/partition_info.out b/src/test/regress/expected/partition_info.out
index 42b6bc77cad..4defa66e5b3 100644
--- a/src/test/regress/expected/partition_info.out
+++ b/src/test/regress/expected/partition_info.out
@@ -349,3 +349,10 @@ SELECT pg_partition_root('ptif_li_child');
 DROP VIEW ptif_test_view;
 DROP MATERIALIZED VIEW ptif_test_matview;
 DROP TABLE ptif_li_parent, ptif_li_child;
+-- Test about selection of arbiter indexes for partitioned tables with
+-- non-valid index on the parent table
+CREATE TABLE pt (a int PRIMARY KEY) PARTITION BY RANGE (a);
+CREATE TABLE p1 PARTITION OF pt FOR VALUES FROM (1) to (2) PARTITION BY RANGE (a);
+CREATE TABLE p1_1 PARTITION OF p1 FOR VALUES FROM (1) TO (2);
+CREATE UNIQUE INDEX ON ONLY p1 (a);
+INSERT INTO p1 VALUES (1) ON CONFLICT (a) DO NOTHING;
diff --git a/src/test/regress/sql/partition_info.sql b/src/test/regress/sql/partition_info.sql
index b5060bec7f0..2ef65292bab 100644
--- a/src/test/regress/sql/partition_info.sql
+++ b/src/test/regress/sql/partition_info.sql
@@ -127,3 +127,11 @@ SELECT pg_partition_root('ptif_li_child');
 DROP VIEW ptif_test_view;
 DROP MATERIALIZED VIEW ptif_test_matview;
 DROP TABLE ptif_li_parent, ptif_li_child;
+
+-- Test about selection of arbiter indexes for partitioned tables with
+-- non-valid index on the parent table
+CREATE TABLE pt (a int PRIMARY KEY) PARTITION BY RANGE (a);
+CREATE TABLE p1 PARTITION OF pt FOR VALUES FROM (1) to (2) PARTITION BY RANGE (a);
+CREATE TABLE p1_1 PARTITION OF p1 FOR VALUES FROM (1) TO (2);
+CREATE UNIQUE INDEX ON ONLY p1 (a);
+INSERT INTO p1 VALUES (1) ON CONFLICT (a) DO NOTHING;