diff --git a/src/backend/executor/nodeMerge.c b/src/backend/executor/nodeMerge.c
index 0e0d0795d4..b21e69903d 100644
--- a/src/backend/executor/nodeMerge.c
+++ b/src/backend/executor/nodeMerge.c
@@ -485,7 +485,7 @@ ExecMerge(ModifyTableState *mtstate, EState *estate, TupleTableSlot *slot,
 	ItemPointer tupleid;
 	ItemPointerData tuple_ctid;
 	bool		matched = false;
-	char		relkind;
+	char		relkind PG_USED_FOR_ASSERTS_ONLY;
 	Datum		datum;
 	bool		isNull;