diff --git a/src/backend/access/nbtree/nbtsort.c b/src/backend/access/nbtree/nbtsort.c
index e6b72111363..efee86784bb 100644
--- a/src/backend/access/nbtree/nbtsort.c
+++ b/src/backend/access/nbtree/nbtsort.c
@@ -1192,7 +1192,7 @@ _bt_load(BTWriteState *wstate, BTSpool *btspool, BTSpool *btspool2)
 	int64		tuples_done = 0;
 	bool		deduplicate;
 
-	deduplicate = wstate->inskey->allequalimage &&
+	deduplicate = wstate->inskey->allequalimage && !btspool->isunique &&
 		BTGetDeduplicateItems(wstate->index);
 
 	if (merge)