diff --git a/core/modules/config/tests/config_test/config/schema/config_test.schema.yml b/core/modules/config/tests/config_test/config/schema/config_test.schema.yml
index 65787afd7a..2cd68a4361 100644
--- a/core/modules/config/tests/config_test/config/schema/config_test.schema.yml
+++ b/core/modules/config/tests/config_test/config/schema/config_test.schema.yml
@@ -162,6 +162,9 @@ config_test.bar:
 config_test.validation:
   type: config_object
   label: 'Configuration type'
+  constraints:
+    Callback:
+      callback: [\Drupal\config_test\ConfigValidation, validateMapping]
   mapping:
     llama:
       type: string
@@ -183,6 +186,9 @@ config_test.validation:
               callback: [\Drupal\config_test\ConfigValidation, validateCatCount]
     giraffe:
       type: sequence
+      constraints:
+        Callback:
+          callback: [\Drupal\config_test\ConfigValidation, validateSequence]
       sequence:
         type: string
         constraints:
diff --git a/core/modules/config/tests/config_test/src/ConfigValidation.php b/core/modules/config/tests/config_test/src/ConfigValidation.php
index e11bfed3e8..d076dbf747 100644
--- a/core/modules/config/tests/config_test/src/ConfigValidation.php
+++ b/core/modules/config/tests/config_test/src/ConfigValidation.php
@@ -64,5 +64,33 @@ public static function validateGiraffes($string, ExecutionContextInterface $cont
       $context->addViolation('Giraffes just hum');
     }
   }
+ 
+  /**
+   * Validates a mapping.
+   *
+   * @param array $mapping
+   *   The data to validate.
+   * @param \Symfony\Component\Validator\Context\ExecutionContextInterface $context
+   *   The validation execution context.
+   */
+  public static function validateMapping($mapping, ExecutionContextInterface $context) {
+    if ($diff = array_diff(array_keys($mapping), ['llama', 'cat', 'giraffe', '_core'])) {
+      $context->addViolation('Missing giraffe.');
+    }
+  }
+
+  /**
+   * Validates a sequence.
+   *
+   * @param array $sequence
+   *   The data to validate.
+   * @param \Symfony\Component\Validator\Context\ExecutionContextInterface $context
+   *   The validation execution context.
+   */
+  public static function validateSequence($sequence, ExecutionContextInterface $context) {
+    if (isset($sequence['invalid-key'])) {
+      $context->addViolation('Invalid giraffe key.');
+    }
+  }
 
 }
diff --git a/core/tests/Drupal/KernelTests/Config/TypedConfigTest.php b/core/tests/Drupal/KernelTests/Config/TypedConfigTest.php
index 6e9b7f9c91..5881a14412 100644
--- a/core/tests/Drupal/KernelTests/Config/TypedConfigTest.php
+++ b/core/tests/Drupal/KernelTests/Config/TypedConfigTest.php
@@ -112,15 +112,35 @@ public function testSimpleConfigValidation() {
     $this->assertCount(1, $result);
     $this->assertEquals('no valid cat', $result->get(0)->getMessage());
 
-    // Test constrains on sequences.
+    // Test constrains on sequences elements.
     $config->set('cat.type', 'nyans');
     $config->set('giraffe', ['muh', 'hum2']);
     $config->save();
-
     $typed_config = $typed_config_manager->get('config_test.validation');
     $result = $typed_config->validate();
     $this->assertCount(1, $result);
     $this->assertEquals('Giraffes just hum', $result->get(0)->getMessage());
+
+    // Test constrains on the sequence itself.
+    $config->set('giraffe', ['hum', 'hum2', 'invalid-key' => 'hum']);
+    $config->save();
+
+    $typed_config = $typed_config_manager->get('config_test.validation');
+    $result = $typed_config->validate();
+    $this->assertCount(1, $result);
+    $this->assertEquals('giraffe', $result->get(0)->getPropertyPath());
+    $this->assertEquals('Invalid giraffe key.', $result->get(0)->getMessage());
+
+    // Validates mapping.
+    $typed_config = $typed_config_manager->get('config_test.validation');
+    $value = $typed_config->getValue();
+    unset($value['giraffe']);
+    $value['elephant'] = 'foo';
+    $typed_config->setValue($value);
+    $result = $typed_config->validate();
+    $this->assertCount(1, $result);
+    $this->assertEquals('', $result->get(0)->getPropertyPath());
+    $this->assertEquals('Missing giraffe.', $result->get(0)->getMessage());
   }
 
 }