diff --git a/core/lib/Drupal/Core/Config/Plugin/Validation/Constraint/LangcodeRequiredIfTranslatableValuesConstraintValidator.php b/core/lib/Drupal/Core/Config/Plugin/Validation/Constraint/LangcodeRequiredIfTranslatableValuesConstraintValidator.php
index 89a45e7b18dcd51501771691d2d894d750bd921a..b28fbac753ddd2b45f05c932bc244e359c7c4ef9 100644
--- a/core/lib/Drupal/Core/Config/Plugin/Validation/Constraint/LangcodeRequiredIfTranslatableValuesConstraintValidator.php
+++ b/core/lib/Drupal/Core/Config/Plugin/Validation/Constraint/LangcodeRequiredIfTranslatableValuesConstraintValidator.php
@@ -22,8 +22,12 @@ public function validate(mixed $value, Constraint $constraint): void {
 
     $mapping = $this->context->getObject();
     assert($mapping instanceof Mapping);
-    if ($mapping !== $this->context->getRoot()) {
-      throw new LogicException('The LangcodeRequiredIfTranslatableValues constraint can only operate on the root object being validated.');
+    $root = $this->context->getRoot();
+    if ($mapping !== $root) {
+      throw new LogicException(sprintf(
+        'The LangcodeRequiredIfTranslatableValues constraint is applied to \'%s\'. This constraint can only operate on the root object being validated.',
+        $root->getName() . '::' . $mapping->getName()
+      ));
     }
 
     assert(in_array('langcode', $mapping->getValidKeys(), TRUE));
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 99b7cfd8f06485340e380d34c69ca1109b176dec..aeac1edea7565abdb4404fce4ea38acf6579bb68 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
@@ -241,6 +241,13 @@ config_test.foo:
     label:
       type: label
       label: 'Label'
+    # Note that config_object should never be used on a non-root key.
+    broken_langcode_required:
+      type: config_object
+      required: false
+      mapping:
+        foo:
+          type: string
 
 config_test.bar:
   type: config_test.foo
diff --git a/core/tests/Drupal/KernelTests/Core/Config/ConfigSchemaTest.php b/core/tests/Drupal/KernelTests/Core/Config/ConfigSchemaTest.php
index 85340992c89e4cb70095bee7cc2033cc53bf7263..57b1cf095653e53a6d8b60d06ab50402f29427c7 100644
--- a/core/tests/Drupal/KernelTests/Core/Config/ConfigSchemaTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Config/ConfigSchemaTest.php
@@ -848,4 +848,15 @@ public function testConfigSaveWithWrappingSchemaDoubleBrackets(): void {
     ], $definition['mapping']['breed']);
   }
 
+  public function testLangcodeRequiredIfTranslatableValuesConstraintError(): void {
+    $config = \Drupal::configFactory()->getEditable('config_test.foo');
+
+    $this->expectException(\LogicException::class);
+    $this->expectExceptionMessage('The LangcodeRequiredIfTranslatableValues constraint is applied to \'config_test.foo::broken_langcode_required\'. This constraint can only operate on the root object being validated.');
+
+    $config
+      ->set('broken_langcode_required.foo', 'bar')
+      ->save();
+  }
+
 }