diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 38f9ffcd04f..265dcfe7fda 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -22815,6 +22815,15 @@ createPartitionTable(List **wqueue, RangeVar *newPartName,
 	 */
 	CommandCounterIncrement();
 
+	/*
+	 * Create a TOAST table if the table needs one.  MERGE/SPLIT PARTITION
+	 * moves rows from existing partition(s) into new partition(s), which may
+	 * carry out-of-line varlena values that the new relation must be able to
+	 * store.  Also, the new partition must be able to receive out-of-line
+	 * varlena values after the DDL operation is complete.
+	 */
+	NewRelationCreateToastTable(newRelId, (Datum) 0);
+
 	/*
 	 * Open the new partition with no lock, because we already have an
 	 * AccessExclusiveLock placed there after creation.
diff --git a/src/test/regress/expected/partition_merge.out b/src/test/regress/expected/partition_merge.out
index d3818f1bf9b..4f42afc3dc7 100644
--- a/src/test/regress/expected/partition_merge.out
+++ b/src/test/regress/expected/partition_merge.out
@@ -1088,6 +1088,32 @@ SELECT count(*) FROM t WHERE i = 15 AND g IN (SELECT g + 10 FROM t WHERE i = 5);
      1
 (1 row)
 
+DROP TABLE t;
+-- A merged partition needs its own TOAST table; otherwise an out-of-line
+-- varlena value carried over from one of the merging partitions has
+-- nowhere to be stored.  SET STORAGE EXTERNAL forces externalization
+-- for any value over the TOAST threshold, so a string over that threshold
+-- suffices to exercise the toast-table dependency.
+CREATE TABLE t (a text) PARTITION BY RANGE(a);
+ALTER TABLE t ALTER COLUMN a SET STORAGE EXTERNAL;
+CREATE TABLE tp_def PARTITION OF t DEFAULT;
+CREATE TABLE tp_2_3 PARTITION OF t FOR VALUES FROM ('2') TO ('3');
+INSERT INTO t SELECT repeat('1', 10000);
+ALTER TABLE t MERGE PARTITIONS (tp_def, tp_2_3) INTO tp_merged;
+SELECT reltoastrelid <> 0 AS has_toast,
+       pg_relation_size(reltoastrelid) > 0 AS toast_used
+  FROM pg_class WHERE relname = 'tp_merged';
+ has_toast | toast_used 
+-----------+------------
+ t         | t
+(1 row)
+
+SELECT length(a) FROM t;
+ length 
+--------
+  10000
+(1 row)
+
 DROP TABLE t;
 RESET search_path;
 --
diff --git a/src/test/regress/expected/partition_split.out b/src/test/regress/expected/partition_split.out
index ff6027af658..faaf32ed20a 100644
--- a/src/test/regress/expected/partition_split.out
+++ b/src/test/regress/expected/partition_split.out
@@ -1653,6 +1653,36 @@ SELECT count(*) FROM t WHERE i = 0 AND tab_id IN (SELECT tab_id FROM t WHERE i =
      0
 (1 row)
 
+DROP TABLE t;
+-- Each new partition produced by SPLIT must get its own TOAST table so
+-- that out-of-line varlena attributes coming from the source partition
+-- can be stored.  SET STORAGE EXTERNAL forces externalization for any
+-- value over the TOAST threshold, so a string over that threshold
+-- suffices to exercise the toast-table dependency.
+CREATE TABLE t (a text) PARTITION BY RANGE(a);
+ALTER TABLE t ALTER COLUMN a SET STORAGE EXTERNAL;
+CREATE TABLE tp_all PARTITION OF t FOR VALUES FROM (MINVALUE) TO (MAXVALUE);
+INSERT INTO t SELECT repeat('1', 10000);
+ALTER TABLE t SPLIT PARTITION tp_all INTO (
+    PARTITION tp_lo FOR VALUES FROM (MINVALUE) TO ('2'),
+    PARTITION tp_hi FOR VALUES FROM ('2') TO (MAXVALUE)
+);
+SELECT relname,
+       reltoastrelid <> 0 AS has_toast,
+       pg_relation_size(reltoastrelid) > 0 AS toast_used
+  FROM pg_class WHERE relname IN ('tp_lo', 'tp_hi') ORDER BY relname;
+ relname | has_toast | toast_used 
+---------+-----------+------------
+ tp_hi   | t         | f
+ tp_lo   | t         | t
+(2 rows)
+
+SELECT length(a) FROM t;
+ length 
+--------
+  10000
+(1 row)
+
 DROP TABLE t;
 RESET search_path;
 --
diff --git a/src/test/regress/sql/partition_merge.sql b/src/test/regress/sql/partition_merge.sql
index 1e14ed40f5c..4c8c625f97b 100644
--- a/src/test/regress/sql/partition_merge.sql
+++ b/src/test/regress/sql/partition_merge.sql
@@ -781,6 +781,23 @@ SELECT count(*) FROM t WHERE i = 15 AND g IN (SELECT g + 10 FROM t WHERE i = 5);
 
 DROP TABLE t;
 
+-- A merged partition needs its own TOAST table; otherwise an out-of-line
+-- varlena value carried over from one of the merging partitions has
+-- nowhere to be stored.  SET STORAGE EXTERNAL forces externalization
+-- for any value over the TOAST threshold, so a string over that threshold
+-- suffices to exercise the toast-table dependency.
+CREATE TABLE t (a text) PARTITION BY RANGE(a);
+ALTER TABLE t ALTER COLUMN a SET STORAGE EXTERNAL;
+CREATE TABLE tp_def PARTITION OF t DEFAULT;
+CREATE TABLE tp_2_3 PARTITION OF t FOR VALUES FROM ('2') TO ('3');
+INSERT INTO t SELECT repeat('1', 10000);
+ALTER TABLE t MERGE PARTITIONS (tp_def, tp_2_3) INTO tp_merged;
+SELECT reltoastrelid <> 0 AS has_toast,
+       pg_relation_size(reltoastrelid) > 0 AS toast_used
+  FROM pg_class WHERE relname = 'tp_merged';
+SELECT length(a) FROM t;
+DROP TABLE t;
+
 
 RESET search_path;
 
diff --git a/src/test/regress/sql/partition_split.sql b/src/test/regress/sql/partition_split.sql
index 05de24152d1..9e44aa9caf0 100644
--- a/src/test/regress/sql/partition_split.sql
+++ b/src/test/regress/sql/partition_split.sql
@@ -1184,6 +1184,25 @@ SELECT count(*) FROM t WHERE i = 0 AND tab_id IN (SELECT tab_id FROM t WHERE i =
 
 DROP TABLE t;
 
+-- Each new partition produced by SPLIT must get its own TOAST table so
+-- that out-of-line varlena attributes coming from the source partition
+-- can be stored.  SET STORAGE EXTERNAL forces externalization for any
+-- value over the TOAST threshold, so a string over that threshold
+-- suffices to exercise the toast-table dependency.
+CREATE TABLE t (a text) PARTITION BY RANGE(a);
+ALTER TABLE t ALTER COLUMN a SET STORAGE EXTERNAL;
+CREATE TABLE tp_all PARTITION OF t FOR VALUES FROM (MINVALUE) TO (MAXVALUE);
+INSERT INTO t SELECT repeat('1', 10000);
+ALTER TABLE t SPLIT PARTITION tp_all INTO (
+    PARTITION tp_lo FOR VALUES FROM (MINVALUE) TO ('2'),
+    PARTITION tp_hi FOR VALUES FROM ('2') TO (MAXVALUE)
+);
+SELECT relname,
+       reltoastrelid <> 0 AS has_toast,
+       pg_relation_size(reltoastrelid) > 0 AS toast_used
+  FROM pg_class WHERE relname IN ('tp_lo', 'tp_hi') ORDER BY relname;
+SELECT length(a) FROM t;
+DROP TABLE t;
 
 RESET search_path;