diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index 2d5caae..37f72ee 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -1276,7 +1276,7 @@ create_merge_append_path(PlannerInfo *root,
 	pathnode->path.parallel_safe = rel->consider_parallel;
 	pathnode->path.parallel_workers = 0;
 	pathnode->path.pathkeys = pathkeys;
-	pathnode->partitioned_rels = partitioned_rels;
+	pathnode->partitioned_rels = list_copy(partitioned_rels);
 	pathnode->subpaths = subpaths;
 
 	/*