diff --git a/src/backend/cdb/cdbllize.c b/src/backend/cdb/cdbllize.c
index f7db8e65a6bf940e154935352acfb25daf9def12..ef3202daa9dadfb53dc3fce743b20590585df936 100644
--- a/src/backend/cdb/cdbllize.c
+++ b/src/backend/cdb/cdbllize.c
@@ -447,6 +447,12 @@ static Node *ParallelizeCorrelatedSubPlanUpdateFlowMutator(Node *node)
  * 				 	 	 \_SeqScan (no quals)
  * 	This transformed plan can be executed in a parallel setting since the correlation
  * 	is now part of the result node which executes in the same slice as the outer plan node.
+ *
+ * XXX: This relies on the planner to not generate other kinds of scans, like
+ * IndexScans. We don't have the machinery in place to rescan those with different
+ * parameters. We could support e.g. IndexScans as long as the index qual doesn't
+ * refer to the outer parameter, but the planner isn't currently smart enough to
+ * distinguish that, so we just disable index scans altogether in a subplan.
  */
 static Node* ParallelizeCorrelatedSubPlanMutator(Node *node, ParallelizeCorrelatedPlanWalkerContext *ctx)
 {
@@ -475,7 +481,8 @@ static Node* ParallelizeCorrelatedSubPlanMutator(Node *node, ParallelizeCorrelat
 	if (IsA(node, SeqScan)
 		|| IsA(node, AppendOnlyScan)
 		|| IsA(node, AOCSScan)
-		|| IsA(node, ShareInputScan))
+		|| IsA(node, ShareInputScan)
+		|| IsA(node, ExternalScan))
 	{
 		Plan *scanPlan = (Plan *) node;
 		/**
diff --git a/src/test/regress/expected/subselect_gp2.out b/src/test/regress/expected/subselect_gp2.out
new file mode 100644
index 0000000000000000000000000000000000000000..db30d47afe2f90f7c98458aa66d41cce283cbe83
--- /dev/null
+++ b/src/test/regress/expected/subselect_gp2.out
@@ -0,0 +1,32 @@
+-- Test using an external table in a subquery.
+--
+-- We used to have a bug where the scan on the external table was not
+-- broadcast to all nodes, so each segment scanned only its own portion
+-- of the external table, when the scan was in a subquery. In that case,
+-- the count(*) calculated for each value below was 1, but it should be
+-- equal to the number of segments, because this external table produces
+-- the same rows on every segment.
+CREATE EXTERNAL WEB TABLE echotable (c1 int, c2 int, c3 int) EXECUTE
+'echo "1,2,3"; echo "4,5,6";' FORMAT 'TEXT' (DELIMITER ',');
+create table test_ext_foo (c1 int, c2 int4);
+NOTICE:  Table doesn't have 'DISTRIBUTED BY' clause -- Using column named 'c1' as the Greenplum Database data distribution key for this table.
+HINT:  The 'DISTRIBUTED BY' clause determines the distribution of data. Make sure column(s) chosen are the optimal data distribution key to minimize skew.
+insert into test_ext_foo select g, g from generate_series(1, 20) g;
+-- This should return 2 and 5, as the two rows are duplicated in
+-- every segment (assuming you have at least two segments in your
+-- cluster).
+select c2 from echotable group by c2 having count(*) >= 2;
+ c2 
+----
+  2
+  5
+(2 rows)
+
+select * from test_ext_foo as o
+where (select count(*) from echotable as i where i.c2 = o.c2) >= 2;
+ c1 | c2 
+----+----
+  5 |  5
+  2 |  2
+(2 rows)
+
diff --git a/src/test/regress/greenplum_schedule b/src/test/regress/greenplum_schedule
index 0814be6a259aa38c0cb565e4bb863d496294b219..1a230348c2771349b1790320617a7f460403bdcc 100755
--- a/src/test/regress/greenplum_schedule
+++ b/src/test/regress/greenplum_schedule
@@ -32,7 +32,7 @@ test: sort_finish_pending
 
 test: gpdiffcheck gptokencheck information_schema gp_hashagg sequence_gp tidscan
 
-test: rangefuncs_cdb gp_dqa external_table subselect_gp indexjoin distributed_transactions olap_group olap_window_seq with_clause as_alias regex_gp partition1
+test: rangefuncs_cdb gp_dqa external_table subselect_gp subselect_gp2 indexjoin distributed_transactions olap_group olap_window_seq with_clause as_alias regex_gp partition1
 
 # 'partition' runs for a long time, so try to keep it together with other
 # long-running tests. Unfortunately, 'partition' also assumes that there
diff --git a/src/test/regress/sql/subselect_gp2.sql b/src/test/regress/sql/subselect_gp2.sql
new file mode 100644
index 0000000000000000000000000000000000000000..790ba89251f4050aaddceb1971610ac342d828b4
--- /dev/null
+++ b/src/test/regress/sql/subselect_gp2.sql
@@ -0,0 +1,22 @@
+-- Test using an external table in a subquery.
+--
+-- We used to have a bug where the scan on the external table was not
+-- broadcast to all nodes, so each segment scanned only its own portion
+-- of the external table, when the scan was in a subquery. In that case,
+-- the count(*) calculated for each value below was 1, but it should be
+-- equal to the number of segments, because this external table produces
+-- the same rows on every segment.
+
+CREATE EXTERNAL WEB TABLE echotable (c1 int, c2 int, c3 int) EXECUTE
+'echo "1,2,3"; echo "4,5,6";' FORMAT 'TEXT' (DELIMITER ',');
+
+create table test_ext_foo (c1 int, c2 int4);
+insert into test_ext_foo select g, g from generate_series(1, 20) g;
+
+-- This should return 2 and 5, as the two rows are duplicated in
+-- every segment (assuming you have at least two segments in your
+-- cluster).
+select c2 from echotable group by c2 having count(*) >= 2;
+
+select * from test_ext_foo as o
+where (select count(*) from echotable as i where i.c2 = o.c2) >= 2;