diff --git a/src/backend/parser/parse_utilcmd.c b/src/backend/parser/parse_utilcmd.c
index 5d2329ddc26..46d2803aa84 100644
--- a/src/backend/parser/parse_utilcmd.c
+++ b/src/backend/parser/parse_utilcmd.c
@@ -3563,7 +3563,6 @@ transformPartitionCmd(CreateStmtContext *cxt, PartitionCmd *cmd)
 			break;
 		case RELKIND_PARTITIONED_INDEX:
 			/* nothing to check */
-			Assert(cmd->bound == NULL);
 			break;
 		case RELKIND_RELATION:
 			/* the table must be partitioned */
diff --git a/src/test/regress/expected/indexing.out b/src/test/regress/expected/indexing.out
index 6a21c0c2e19..c7822a4c585 100644
--- a/src/test/regress/expected/indexing.out
+++ b/src/test/regress/expected/indexing.out
@@ -94,6 +94,22 @@ Partition of: idxparti2
 No partition constraint
 btree, for table "public.idxpart1"
 
+-- ALTER TABLE when attaching or detaching an index to a partition.
+create index idxpart_c on only idxpart (c);
+create index idxpart1_c on idxpart1 (c);
+alter table idxpart_c attach partition idxpart1_c for values from (10) to (20);
+alter index idxpart_c attach partition idxpart1_c;
+select relname, relpartbound from pg_class
+  where relname in ('idxpart_c', 'idxpart1_c')
+  order by relname;
+  relname   | relpartbound 
+------------+--------------
+ idxpart1_c | 
+ idxpart_c  | 
+(2 rows)
+
+alter table idxpart_c detach partition idxpart1_c;
+ERROR:  "idxpart_c" is not a table
 drop table idxpart;
 -- If a partition already has an index, don't create a duplicative one
 create table idxpart (a int, b int) partition by range (a, b);
diff --git a/src/test/regress/sql/indexing.sql b/src/test/regress/sql/indexing.sql
index d14d9f85287..d87031b3984 100644
--- a/src/test/regress/sql/indexing.sql
+++ b/src/test/regress/sql/indexing.sql
@@ -46,6 +46,16 @@ alter table idxpart attach partition idxpart1 for values from (0) to (10);
 \d idxpart1
 \d+ idxpart1_a_idx
 \d+ idxpart1_b_c_idx
+
+-- ALTER TABLE when attaching or detaching an index to a partition.
+create index idxpart_c on only idxpart (c);
+create index idxpart1_c on idxpart1 (c);
+alter table idxpart_c attach partition idxpart1_c for values from (10) to (20);
+alter index idxpart_c attach partition idxpart1_c;
+select relname, relpartbound from pg_class
+  where relname in ('idxpart_c', 'idxpart1_c')
+  order by relname;
+alter table idxpart_c detach partition idxpart1_c;
 drop table idxpart;
 
 -- If a partition already has an index, don't create a duplicative one