diff --git a/src/backend/catalog/aclchk.c b/src/backend/catalog/aclchk.c
index 13785add07f..4befcb797dd 100644
--- a/src/backend/catalog/aclchk.c
+++ b/src/backend/catalog/aclchk.c
@@ -1328,6 +1328,9 @@ SetDefaultACL(InternalDefaultACL *iacls)
 		ReleaseSysCache(tuple);
 
 	heap_close(rel, RowExclusiveLock);
+
+	/* prevent error when processing duplicate objects */
+	CommandCounterIncrement();
 }
 
 
diff --git a/src/test/regress/expected/privileges.out b/src/test/regress/expected/privileges.out
index 46f11c241ff..ada059244ac 100644
--- a/src/test/regress/expected/privileges.out
+++ b/src/test/regress/expected/privileges.out
@@ -1581,7 +1581,8 @@ SELECT has_table_privilege('regress_user1', 'testns.acltest1', 'INSERT'); -- no
  f
 (1 row)
 
-ALTER DEFAULT PRIVILEGES IN SCHEMA testns GRANT SELECT ON TABLES TO public;
+-- placeholder for test with duplicated schema and role names
+ALTER DEFAULT PRIVILEGES IN SCHEMA testns,testns GRANT SELECT ON TABLES TO public,public;
 SELECT has_table_privilege('regress_user1', 'testns.acltest1', 'SELECT'); -- no
  has_table_privilege 
 ---------------------
diff --git a/src/test/regress/sql/privileges.sql b/src/test/regress/sql/privileges.sql
index 968704a8f55..7edfc28f845 100644
--- a/src/test/regress/sql/privileges.sql
+++ b/src/test/regress/sql/privileges.sql
@@ -942,7 +942,8 @@ CREATE TABLE testns.acltest1 (x int);
 SELECT has_table_privilege('regress_user1', 'testns.acltest1', 'SELECT'); -- no
 SELECT has_table_privilege('regress_user1', 'testns.acltest1', 'INSERT'); -- no
 
-ALTER DEFAULT PRIVILEGES IN SCHEMA testns GRANT SELECT ON TABLES TO public;
+-- placeholder for test with duplicated schema and role names
+ALTER DEFAULT PRIVILEGES IN SCHEMA testns,testns GRANT SELECT ON TABLES TO public,public;
 
 SELECT has_table_privilege('regress_user1', 'testns.acltest1', 'SELECT'); -- no
 SELECT has_table_privilege('regress_user1', 'testns.acltest1', 'INSERT'); -- no