diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index 1c3a9e06d37..05dc6add7eb 100644
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -2989,7 +2989,7 @@ index_build(Relation heapRelation,
 
 	/*
 	 * Determine worker process details for parallel CREATE INDEX.  Currently,
-	 * only btree has support for parallel builds.
+	 * only btree and BRIN have support for parallel builds.
 	 *
 	 * Note that planner considers parallel safety for us.
 	 */
diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index a0a2de7ee4b..f3856c519f6 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -6758,7 +6758,8 @@ plan_cluster_use_sort(Oid tableOid, Oid indexOid)
  *		CREATE INDEX should request for use
  *
  * tableOid is the table on which the index is to be built.  indexOid is the
- * OID of an index to be created or reindexed (which must be a btree index).
+ * OID of an index to be created or reindexed (which must be an index with
+ * support for parallel builds - currently btree or BRIN).
  *
  * Return value is the number of parallel worker processes to request.  It
  * may be unsafe to proceed if this is 0.  Note that this does not include the