diff --git a/src/backend/partitioning/partbounds.c b/src/backend/partitioning/partbounds.c
index a09beec34d8..73dea0375be 100644
--- a/src/backend/partitioning/partbounds.c
+++ b/src/backend/partitioning/partbounds.c
@@ -5419,7 +5419,8 @@ check_partition_bounds_for_split_range(Relation parent,
 								"ALTER TABLE ... SPLIT PARTITION"),
 						parser_errposition(pstate, exprLocation((Node *) datum)));
 		}
-		else
+
+		if (last)
 		{
 			PartitionRangeBound *split_upper;
 
diff --git a/src/test/regress/expected/partition_split.out b/src/test/regress/expected/partition_split.out
index 961b37953c8..a2ccbe5138b 100644
--- a/src/test/regress/expected/partition_split.out
+++ b/src/test/regress/expected/partition_split.out
@@ -1188,6 +1188,22 @@ SELECT tableoid::regclass, * FROM sales_range ORDER BY tableoid::regclass::text
 
 DROP TABLE sales_range;
 --
+-- Test that the explicit partition bound cannot extend outside the split
+-- partition's bound when a DEFAULT partition is specified.
+--
+CREATE TABLE t (i int) PARTITION BY RANGE (i);
+CREATE TABLE tp_0_51 PARTITION OF t FOR VALUES FROM (0) TO (51);
+CREATE TABLE tp_51_100 PARTITION OF t FOR VALUES FROM (51) TO (100);
+-- ERROR
+ALTER TABLE t SPLIT PARTITION tp_0_51 INTO
+  (PARTITION tp_0_51 FOR VALUES FROM (0) TO (53),
+   PARTITION tp_default DEFAULT);
+ERROR:  upper bound of partition "tp_0_51" is greater than upper bound of split partition "tp_0_51"
+LINE 2:   (PARTITION tp_0_51 FOR VALUES FROM (0) TO (53),
+                                                     ^
+HINT:  ALTER TABLE ... SPLIT PARTITION require combined bounds of new partitions must exactly match the bound of the split partition.
+DROP TABLE t;
+--
 -- Try to SPLIT partition of another table.
 --
 CREATE TABLE t1(i int, t text) PARTITION BY LIST (t);
diff --git a/src/test/regress/sql/partition_split.sql b/src/test/regress/sql/partition_split.sql
index a110fc87867..d9821c5e2a3 100644
--- a/src/test/regress/sql/partition_split.sql
+++ b/src/test/regress/sql/partition_split.sql
@@ -834,6 +834,21 @@ SELECT tableoid::regclass, * FROM sales_range ORDER BY tableoid::regclass::text
 
 DROP TABLE sales_range;
 
+--
+-- Test that the explicit partition bound cannot extend outside the split
+-- partition's bound when a DEFAULT partition is specified.
+--
+CREATE TABLE t (i int) PARTITION BY RANGE (i);
+CREATE TABLE tp_0_51 PARTITION OF t FOR VALUES FROM (0) TO (51);
+CREATE TABLE tp_51_100 PARTITION OF t FOR VALUES FROM (51) TO (100);
+
+-- ERROR
+ALTER TABLE t SPLIT PARTITION tp_0_51 INTO
+  (PARTITION tp_0_51 FOR VALUES FROM (0) TO (53),
+   PARTITION tp_default DEFAULT);
+
+DROP TABLE t;
+
 --
 -- Try to SPLIT partition of another table.
 --