diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index 134130476e..fa09a6103b 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -7093,38 +7093,36 @@ make_modifytable(PlannerInfo *root, Plan *subplan,
 			RelOptInfo *resultRel = root->simple_rel_array[rti];
 
 			fdwroutine = resultRel->fdwroutine;
-
-			/*
-			 * MERGE is not currently supported for foreign tables and we
-			 * already checked when the table mentioned in the query is
-			 * foreign; but we can still get here if a partitioned table has a
-			 * foreign table as partition.  Disallow that now, to avoid an
-			 * uglier error message later.
-			 */
-			if (operation == CMD_MERGE && fdwroutine != NULL)
-			{
-				RangeTblEntry *rte = root->simple_rte_array[rti];
-
-				ereport(ERROR,
-						errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-						errmsg("cannot execute MERGE on relation \"%s\"",
-							   get_rel_name(rte->relid)),
-						errdetail_relkind_not_supported(rte->relkind));
-			}
-
 		}
 		else
 		{
 			RangeTblEntry *rte = planner_rt_fetch(rti, root);
 
-			Assert(rte->rtekind == RTE_RELATION);
-			Assert(operation != CMD_MERGE);
-			if (rte->relkind == RELKIND_FOREIGN_TABLE)
+			if (rte->rtekind == RTE_RELATION &&
+				rte->relkind == RELKIND_FOREIGN_TABLE)
 				fdwroutine = GetFdwRoutineByRelId(rte->relid);
 			else
 				fdwroutine = NULL;
 		}
 
+		/*
+		 * MERGE is not currently supported for foreign tables.  We already
+		 * checked that when the table mentioned in the query is foreign; but
+		 * we can still get here if a partitioned table has a foreign table as
+		 * partition.  Disallow that now, to avoid an uglier error message
+		 * later.
+		 */
+		if (operation == CMD_MERGE && fdwroutine != NULL)
+		{
+			RangeTblEntry *rte = planner_rt_fetch(rti, root);
+
+			ereport(ERROR,
+					errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					errmsg("cannot execute MERGE on relation \"%s\"",
+						   get_rel_name(rte->relid)),
+					errdetail_relkind_not_supported(rte->relkind));
+		}
+
 		/*
 		 * Try to modify the foreign table directly if (1) the FDW provides
 		 * callback functions needed for that and (2) there are no local