diff --git a/src/backend/commands/copy.c b/src/backend/commands/copy.c
index eca0be1ff96..2593732c16e 100644
--- a/src/backend/commands/copy.c
+++ b/src/backend/commands/copy.c
@@ -2446,6 +2446,9 @@ CopyMultiInsertBufferFlush(CopyMultiInsertInfo *miinfo,
 	ResultRelInfo *resultRelInfo = buffer->resultRelInfo;
 	TupleTableSlot **slots = buffer->slots;
 
+	/* Set es_result_relation_info to the ResultRelInfo we're flushing. */
+	estate->es_result_relation_info = resultRelInfo;
+
 	/*
 	 * Print error context information correctly, if one of the operations
 	 * below fail.
diff --git a/src/backend/executor/execIndexing.c b/src/backend/executor/execIndexing.c
index c41c5f45e7e..40bd8049f05 100644
--- a/src/backend/executor/execIndexing.c
+++ b/src/backend/executor/execIndexing.c
@@ -299,6 +299,9 @@ ExecInsertIndexTuples(TupleTableSlot *slot,
 	indexInfoArray = resultRelInfo->ri_IndexRelationInfo;
 	heapRelation = resultRelInfo->ri_RelationDesc;
 
+	/* Sanity check: slot must belong to the same rel as the resultRelInfo. */
+	Assert(slot->tts_tableOid == RelationGetRelid(heapRelation));
+
 	/*
 	 * We will use the EState's per-tuple context for evaluating predicates
 	 * and index expressions (creating it if it's not already there).
diff --git a/src/test/regress/input/copy.source b/src/test/regress/input/copy.source
index aefc99167af..a1d529ad367 100644
--- a/src/test/regress/input/copy.source
+++ b/src/test/regress/input/copy.source
@@ -187,4 +187,17 @@ copy parted_copytest from '@abs_builddir@/results/parted_copytest.csv';
 select tableoid::regclass,count(*),sum(a) from parted_copytest
 group by tableoid order by tableoid::regclass::name;
 
+truncate table parted_copytest;
+create index on parted_copytest (b);
+drop trigger part_ins_trig on parted_copytest_a2;
+
+copy parted_copytest from stdin;
+1	1	str1
+2	2	str2
+\.
+
+-- Ensure index entries were properly added during the copy.
+select * from parted_copytest where b = 1;
+select * from parted_copytest where b = 2;
+
 drop table parted_copytest;
diff --git a/src/test/regress/output/copy.source b/src/test/regress/output/copy.source
index cf716aeccaa..938d3551da2 100644
--- a/src/test/regress/output/copy.source
+++ b/src/test/regress/output/copy.source
@@ -147,4 +147,21 @@ group by tableoid order by tableoid::regclass::name;
  parted_copytest_a2 |    10 |  10055
 (2 rows)
 
+truncate table parted_copytest;
+create index on parted_copytest (b);
+drop trigger part_ins_trig on parted_copytest_a2;
+copy parted_copytest from stdin;
+-- Ensure index entries were properly added during the copy.
+select * from parted_copytest where b = 1;
+ a | b |  c   
+---+---+------
+ 1 | 1 | str1
+(1 row)
+
+select * from parted_copytest where b = 2;
+ a | b |  c   
+---+---+------
+ 2 | 2 | str2
+(1 row)
+
 drop table parted_copytest;