diff --git a/core/modules/config/tests/config_schema_test/config/schema/config_schema_test.schema.yml b/core/modules/config/tests/config_schema_test/config/schema/config_schema_test.schema.yml
index ce894c2..fcf4048 100644
--- a/core/modules/config/tests/config_schema_test/config/schema/config_schema_test.schema.yml
+++ b/core/modules/config/tests/config_schema_test/config/schema/config_schema_test.schema.yml
@@ -335,3 +335,17 @@ config_schema_test.schema_sequence_sort:
               type: string
             bar:
               type: string
+
+config_schema_test.simple_mapping:
+  type: mapping
+  mapping:
+    base_sequence_item:
+      type: string
+
+config_schema_test.schema_sequence_merged_mapping:
+  type: sequence
+  sequence:
+    type: config_schema_test.simple_mapping
+    mapping:
+      sub_sequence_item:
+        type: string
diff --git a/core/tests/Drupal/KernelTests/Core/Config/ConfigSchemaTest.php b/core/tests/Drupal/KernelTests/Core/Config/ConfigSchemaTest.php
index fb3573e..d391845 100644
--- a/core/tests/Drupal/KernelTests/Core/Config/ConfigSchemaTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Config/ConfigSchemaTest.php
@@ -411,6 +411,23 @@ public function testConfigSaveWithSchema() {
   }
 
   /**
+   * Test config sequence with merged mapping.
+   */
+  public function testConfigSequenceWithMergedMapping() {
+    $data = [
+      [
+        'base_sequence_item' => 'foo',
+        'sub_sequence_item' => 'bar',
+      ],
+    ];
+    $this->config('config_schema_test.schema_sequence_merged_mapping')
+      ->setData($data)
+      ->save();
+
+    $this->assertEquals($data, $this->config('config_schema_test.schema_sequence_sort')->get());
+  }
+
+  /**
    * Tests configuration sequence sorting using schemas.
    */
   public function testConfigSaveWithSequenceSorting() {