diff --git a/src/backend/commands/indexcmds.c b/src/backend/commands/indexcmds.c
index 504806b25b..ff40683d06 100644
--- a/src/backend/commands/indexcmds.c
+++ b/src/backend/commands/indexcmds.c
@@ -973,7 +973,7 @@ DefineIndex(Oid relationId,
 								InvalidOid,			/* no predefined OID */
 								indexRelationId,	/* this is our child */
 								createdConstraintId,
-								false, check_rights, check_not_in_use,
+								is_alter_table, check_rights, check_not_in_use,
 								false, quiet);
 				}
 
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 46a648a33a..218224a156 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -14256,7 +14256,7 @@ AttachPartitionEnsureIndexes(Relation rel, Relation attachrel)
 			DefineIndex(RelationGetRelid(attachrel), stmt, InvalidOid,
 						RelationGetRelid(idxRel),
 						constraintOid,
-						false, false, false, false, false);
+						true, false, false, false, false);
 		}
 
 		index_close(idxRel, AccessShareLock);
diff --git a/src/test/regress/expected/indexing.out b/src/test/regress/expected/indexing.out
index 3fa47cba96..fb32ffffdc 100644
--- a/src/test/regress/expected/indexing.out
+++ b/src/test/regress/expected/indexing.out
@@ -878,7 +878,7 @@ select conname, contype, conrelid::regclass, conindid::regclass, conkey
 
 drop table idxpart;
 -- Verify that multi-layer partitioning honors the requirement that all
--- columns in the partition key must appear in primary key
+-- columns in the partition key must appear in primary/unique key
 create table idxpart (a int, b int, primary key (a)) partition by range (a);
 create table idxpart2 partition of idxpart
 for values from (0) to (1000) partition by range (b); -- fail
@@ -886,12 +886,12 @@ ERROR:  insufficient columns in PRIMARY KEY constraint definition
 DETAIL:  PRIMARY KEY constraint on table "idxpart2" lacks column "b" which is part of the partition key.
 drop table idxpart;
 -- Ditto for the ATTACH PARTITION case
-create table idxpart (a int primary key, b int) partition by range (a);
-create table idxpart1 (a int not null, b int, primary key (a, b))
+create table idxpart (a int unique, b int) partition by range (a);
+create table idxpart1 (a int not null, b int, unique (a, b))
   partition by range (a, b);
 alter table idxpart attach partition idxpart1 for values from (1) to (1000);
-ERROR:  insufficient columns in PRIMARY KEY constraint definition
-DETAIL:  PRIMARY KEY constraint on table "idxpart1" lacks column "b" which is part of the partition key.
+ERROR:  insufficient columns in UNIQUE constraint definition
+DETAIL:  UNIQUE constraint on table "idxpart1" lacks column "b" which is part of the partition key.
 DROP TABLE idxpart, idxpart1;
 -- Multi-layer partitioning works correctly in this case:
 create table idxpart (a int, b int, primary key (a, b)) partition by range (a);
@@ -952,6 +952,22 @@ select indrelid::regclass, indexrelid::regclass, inhparent::regclass, indisvalid
 (0 rows)
 
 drop table idxpart;
+-- If the partition to be attached already has a primary key, fail if
+-- it doesn't match the parent's PK.
+CREATE TABLE idxpart (c1 INT PRIMARY KEY, c2 INT, c3 VARCHAR(10)) PARTITION BY RANGE(c1);
+CREATE TABLE idxpart1 (LIKE idxpart);
+ALTER TABLE idxpart1 ADD PRIMARY KEY (c1, c2);
+ALTER TABLE idxpart ATTACH PARTITION idxpart1 FOR VALUES FROM (100) TO (200);
+ERROR:  multiple primary keys for table "idxpart1" are not allowed
+DROP TABLE idxpart, idxpart1;
+-- Ditto if there is some distance between the PKs (subpartitioning)
+create table idxpart (a int, b int, primary key (a)) partition by range (a);
+create table idxpart1 (a int not null, b int) partition by range (a);
+create table idxpart11 (a int not null, b int primary key);
+alter table idxpart1 attach partition idxpart11 for values from (0) to (1000);
+alter table idxpart attach partition idxpart1 for values from (0) to (10000);
+ERROR:  multiple primary keys for table "idxpart11" are not allowed
+drop table idxpart, idxpart1, idxpart11;
 -- If a partitioned table has a constraint whose index is not valid,
 -- attaching a missing partition makes it valid.
 create table idxpart (a int) partition by range (a);
diff --git a/src/test/regress/sql/indexing.sql b/src/test/regress/sql/indexing.sql
index 902d8c59ca..c4ab89fc48 100644
--- a/src/test/regress/sql/indexing.sql
+++ b/src/test/regress/sql/indexing.sql
@@ -444,15 +444,15 @@ select conname, contype, conrelid::regclass, conindid::regclass, conkey
 drop table idxpart;
 
 -- Verify that multi-layer partitioning honors the requirement that all
--- columns in the partition key must appear in primary key
+-- columns in the partition key must appear in primary/unique key
 create table idxpart (a int, b int, primary key (a)) partition by range (a);
 create table idxpart2 partition of idxpart
 for values from (0) to (1000) partition by range (b); -- fail
 drop table idxpart;
 
 -- Ditto for the ATTACH PARTITION case
-create table idxpart (a int primary key, b int) partition by range (a);
-create table idxpart1 (a int not null, b int, primary key (a, b))
+create table idxpart (a int unique, b int) partition by range (a);
+create table idxpart1 (a int not null, b int, unique (a, b))
   partition by range (a, b);
 alter table idxpart attach partition idxpart1 for values from (1) to (1000);
 DROP TABLE idxpart, idxpart1;
@@ -494,6 +494,22 @@ select indrelid::regclass, indexrelid::regclass, inhparent::regclass, indisvalid
   order by indexrelid::regclass::text collate "C";
 drop table idxpart;
 
+-- If the partition to be attached already has a primary key, fail if
+-- it doesn't match the parent's PK.
+CREATE TABLE idxpart (c1 INT PRIMARY KEY, c2 INT, c3 VARCHAR(10)) PARTITION BY RANGE(c1);
+CREATE TABLE idxpart1 (LIKE idxpart);
+ALTER TABLE idxpart1 ADD PRIMARY KEY (c1, c2);
+ALTER TABLE idxpart ATTACH PARTITION idxpart1 FOR VALUES FROM (100) TO (200);
+DROP TABLE idxpart, idxpart1;
+
+-- Ditto if there is some distance between the PKs (subpartitioning)
+create table idxpart (a int, b int, primary key (a)) partition by range (a);
+create table idxpart1 (a int not null, b int) partition by range (a);
+create table idxpart11 (a int not null, b int primary key);
+alter table idxpart1 attach partition idxpart11 for values from (0) to (1000);
+alter table idxpart attach partition idxpart1 for values from (0) to (10000);
+drop table idxpart, idxpart1, idxpart11;
+
 -- If a partitioned table has a constraint whose index is not valid,
 -- attaching a missing partition makes it valid.
 create table idxpart (a int) partition by range (a);