diff --git a/src/backend/utils/sort/tuplesort.c b/src/backend/utils/sort/tuplesort.c
index 015c197a77f..d1c29b2f043 100644
--- a/src/backend/utils/sort/tuplesort.c
+++ b/src/backend/utils/sort/tuplesort.c
@@ -4775,6 +4775,7 @@ writetup_datum(Tuplesortstate *state, int tapenum, SortTuple *stup)
 	{
 		FREEMEM(state, GetMemoryChunkSpace(stup->tuple));
 		pfree(stup->tuple);
+		stup->tuple = NULL;
 	}
 }