diff --git a/src/backend/partitioning/partprune.c b/src/backend/partitioning/partprune.c
index 2efb2c864de..f128b99c36a 100644
--- a/src/backend/partitioning/partprune.c
+++ b/src/backend/partitioning/partprune.c
@@ -46,6 +46,7 @@
 #include "nodes/makefuncs.h"
 #include "nodes/nodeFuncs.h"
 #include "optimizer/appendinfo.h"
+#include "optimizer/clauses.h"
 #include "optimizer/cost.h"
 #include "optimizer/optimizer.h"
 #include "optimizer/pathnode.h"
@@ -2073,7 +2074,11 @@ match_clause_to_partition_key(GeneratePruningStepsContext *context,
 
 			/*
 			 * See if there are any exec Params.  If so, we can only use this
-			 * expression during per-scan pruning.
+			 * expression during per-scan pruning.  The same is true if it
+			 * contains a SubPlan, as evaluating that requires the parent
+			 * node's PlanState, which startup-time pruning hasn't got.  (A
+			 * SubPlan's testexpr normally contains exec Params, so we'd have
+			 * caught it above, but the testexpr can be folded to a Const.)
 			 */
 			paramids = pull_exec_paramids(expr);
 			if (!bms_is_empty(paramids))
@@ -2082,6 +2087,11 @@ match_clause_to_partition_key(GeneratePruningStepsContext *context,
 				if (context->target != PARTTARGET_EXEC)
 					return PARTCLAUSE_UNSUPPORTED;
 			}
+			else if (contain_subplans((Node *) expr))
+			{
+				if (context->target != PARTTARGET_EXEC)
+					return PARTCLAUSE_UNSUPPORTED;
+			}
 			else
 			{
 				/* It's potentially usable, but mutable */
diff --git a/src/test/regress/expected/partition_prune.out b/src/test/regress/expected/partition_prune.out
index 191901210a8..3506ecec477 100644
--- a/src/test/regress/expected/partition_prune.out
+++ b/src/test/regress/expected/partition_prune.out
@@ -2106,6 +2106,22 @@ where asptab.id > ss.b::int;
      ->  Seq Scan on int4_tbl tinner
 (14 rows)
 
+-- check that a SubPlan in a pruning expression is not used for startup-time
+-- pruning, which has no parent PlanState to evaluate the SubPlan with
+explain (costs off)
+select * from asptab where id = (null::int in (select f1 from int4_tbl))::int;
+                          QUERY PLAN                          
+--------------------------------------------------------------
+ Append
+   ->  Index Only Scan using asptab0_pkey on asptab0 asptab_1
+         Index Cond: (id = ((ANY NULL::boolean))::integer)
+         SubPlan any_1
+           ->  Materialize
+                 ->  Seq Scan on int4_tbl
+   ->  Index Only Scan using asptab1_pkey on asptab1 asptab_2
+         Index Cond: (id = ((ANY NULL::boolean))::integer)
+(8 rows)
+
 drop table asptab;
 --
 -- Test Partition pruning for HASH partitioning
diff --git a/src/test/regress/sql/partition_prune.sql b/src/test/regress/sql/partition_prune.sql
index 01f44538fb6..d6e096dc565 100644
--- a/src/test/regress/sql/partition_prune.sql
+++ b/src/test/regress/sql/partition_prune.sql
@@ -488,6 +488,12 @@ select * from
   asptab
 where asptab.id > ss.b::int;
 
+-- check that a SubPlan in a pruning expression is not used for startup-time
+-- pruning, which has no parent PlanState to evaluate the SubPlan with
+
+explain (costs off)
+select * from asptab where id = (null::int in (select f1 from int4_tbl))::int;
+
 drop table asptab;
 
 --