diff --git a/src/backend/utils/sort/tuplesort.c b/src/backend/utils/sort/tuplesort.c
index 510565c339..ae384a8546 100644
--- a/src/backend/utils/sort/tuplesort.c
+++ b/src/backend/utils/sort/tuplesort.c
@@ -1443,7 +1443,7 @@ tuplesort_putindextuplevalues(Tuplesortstate *state, Relation rel,
 			mtup->datum1 = index_getattr(tuple,
 										 1,
 										 RelationGetDescr(state->indexRel),
-										 &stup.isnull1);
+										 &mtup->isnull1);
 		}
 	}
 
@@ -4271,7 +4271,7 @@ copytup_cluster(Tuplesortstate *state, SortTuple *stup, void *tup)
 			mtup->datum1 = heap_getattr(tuple,
 									  state->indexInfo->ii_KeyAttrNumbers[0],
 										state->tupDesc,
-										&stup->isnull1);
+										&mtup->isnull1);
 		}
 	}
 }
@@ -4588,7 +4588,7 @@ copytup_index(Tuplesortstate *state, SortTuple *stup, void *tup)
 			mtup->datum1 = index_getattr(tuple,
 										 1,
 										 RelationGetDescr(state->indexRel),
-										 &stup->isnull1);
+										 &mtup->isnull1);
 		}
 	}
 }