diff --git a/src/backend/catalog/aclchk.c b/src/backend/catalog/aclchk.c
index a82aa516a63..9fd1cc2d42a 100644
--- a/src/backend/catalog/aclchk.c
+++ b/src/backend/catalog/aclchk.c
@@ -5687,9 +5687,9 @@ recordExtObjInitPriv(Oid objoid, Oid classoid)
 
 		ReleaseSysCache(tuple);
 	}
-	/* pg_largeobject_metadata */
-	else if (classoid == LargeObjectMetadataRelationId)
+	else if (classoid == LargeObjectRelationId)
 	{
+		/* For large objects, we must consult pg_largeobject_metadata */
 		Datum		aclDatum;
 		bool		isNull;
 		HeapTuple	tuple;
diff --git a/src/backend/commands/alter.c b/src/backend/commands/alter.c
index b11ebf0f618..6dc39189721 100644
--- a/src/backend/commands/alter.c
+++ b/src/backend/commands/alter.c
@@ -1044,9 +1044,14 @@ AlterObjectOwner_internal(Relation rel, Oid objectId, Oid new_ownerId)
 		/* Perform actual update */
 		CatalogTupleUpdate(rel, &newtup->t_self, newtup);
 
-		/* Update owner dependency reference */
+		/*
+		 * Update owner dependency reference.  When working on a large object,
+		 * we have to translate back to the OID conventionally used for LOs'
+		 * classId.
+		 */
 		if (classId == LargeObjectMetadataRelationId)
 			classId = LargeObjectRelationId;
+
 		changeDependencyOnOwner(classId, objectId, new_ownerId);
 
 		/* Release memory */
@@ -1054,6 +1059,16 @@ AlterObjectOwner_internal(Relation rel, Oid objectId, Oid new_ownerId)
 		pfree(nulls);
 		pfree(replaces);
 	}
+	else
+	{
+		/*
+		 * No need to change anything.  But when working on a large object, we
+		 * have to translate back to the OID conventionally used for LOs'
+		 * classId, or the post-alter hook (if any) will get confused.
+		 */
+		if (classId == LargeObjectMetadataRelationId)
+			classId = LargeObjectRelationId;
+	}
 
 	InvokeObjectPostAlterHook(classId, objectId, 0);
 }