diff --git a/core/core.services.yml b/core/core.services.yml
index b2f549d867..cd647713cb 100644
--- a/core/core.services.yml
+++ b/core/core.services.yml
@@ -436,8 +436,6 @@ services:
     class: Drupal\Component\Serialization\PhpSerialize
   serialization.yaml:
     class: Drupal\Component\Serialization\Yaml
-    calls:
-      - [setTranslation, ['@string_translation']]
 
   settings:
     class: Drupal\Core\Site\Settings
diff --git a/core/lib/Drupal/Component/Serialization/TaggedSerializationInterface.php b/core/lib/Drupal/Component/Serialization/TaggedSerializationInterface.php
new file mode 100644
index 0000000000..361ea65bf5
--- /dev/null
+++ b/core/lib/Drupal/Component/Serialization/TaggedSerializationInterface.php
@@ -0,0 +1,28 @@
+<?php
+
+namespace Drupal\Component\Serialization;
+
+/**
+ * Class TaggedSerializationInterface.
+ */
+interface TaggedSerializationInterface extends SerializationInterface {
+
+  /**
+   * Retrieves a map of tag callbacks.
+   *
+   * @return array
+   *   An associative array where the key is the tag and the value is the
+   *   callback.
+   */
+  public static function getTagCallbacks();
+
+  /**
+   * Sets a map of tag callbacks.
+   *
+   * @param array $callbacks
+   *   An associative array where the key is the tag and the value is the
+   *   callback.
+   */
+  public static function setTagCallbacks(array $callbacks);
+
+}
diff --git a/core/lib/Drupal/Component/Serialization/TaggedSerializationTrait.php b/core/lib/Drupal/Component/Serialization/TaggedSerializationTrait.php
new file mode 100644
index 0000000000..80a1d91d0c
--- /dev/null
+++ b/core/lib/Drupal/Component/Serialization/TaggedSerializationTrait.php
@@ -0,0 +1,39 @@
+<?php
+
+namespace Drupal\Component\Serialization;
+
+/**
+ * Trait TaggedSerializationTrait.
+ */
+trait TaggedSerializationTrait {
+
+  /**
+   * Associative array of tag callbacks, keyed by tag.
+   *
+   * @var array
+   */
+  protected $tagCallbacks = [];
+
+  /**
+   * Retrieves a map of tag callbacks.
+   *
+   * @return array
+   *   An associative array where the key is the tag and the value is the
+   *   callback.
+   */
+  public static function getTagCallbacks() {
+    return [];
+  }
+
+  /**
+   * Sets a map of tag callbacks.
+   *
+   * @param array $callbacks
+   *   An associative array where the key is the tag and the value is the
+   *   callback.
+   */
+  public static function setTagCallbacks(array $callbacks) {
+    static::$tagCallbacks = $callbacks;
+  }
+
+}
diff --git a/core/lib/Drupal/Component/Serialization/TranslatableSerializationInterface.php b/core/lib/Drupal/Component/Serialization/TranslatableSerializationInterface.php
deleted file mode 100644
index e7a2011108..0000000000
--- a/core/lib/Drupal/Component/Serialization/TranslatableSerializationInterface.php
+++ /dev/null
@@ -1,20 +0,0 @@
-<?php
-
-namespace Drupal\Component\Serialization;
-
-use Drupal\Core\StringTranslation\TranslationInterface;
-
-/**
- * Defines an interface for serialization formats.
- */
-interface TranslatableSerializationInterface extends SerializationInterface {
-
-  /**
-   * Sets the Translation manager.
-   *
-   * @param \Drupal\Core\StringTranslation\TranslationInterface $translation
-   *   The Translation manager.
-   */
-  public static function setTranslation(TranslationInterface $translation);
-
-}
diff --git a/core/lib/Drupal/Component/Serialization/TranslatableSerializationTrait.php b/core/lib/Drupal/Component/Serialization/TranslatableSerializationTrait.php
deleted file mode 100644
index cc0aa02b87..0000000000
--- a/core/lib/Drupal/Component/Serialization/TranslatableSerializationTrait.php
+++ /dev/null
@@ -1,33 +0,0 @@
-<?php
-
-namespace Drupal\Component\Serialization;
-
-use Drupal\Core\StringTranslation\TranslationInterface;
-
-/**
- * Trait TranslatableSerializationTrait.
- */
-trait TranslatableSerializationTrait {
-
-  /**
-   * The Translation Manager.
-   *
-   * @var \Drupal\Core\StringTranslation\TranslationInterface
-   */
-  protected static $translation;
-
-  protected static function getTranslation() {
-    if (!isset(static::$translation)) {
-      static::$translation = \Drupal::translation();
-    }
-    return static::$translation;
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  public static function setTranslation(TranslationInterface $translation) {
-    static::$translation = $translation;
-  }
-
-}
diff --git a/core/lib/Drupal/Component/Serialization/Yaml.php b/core/lib/Drupal/Component/Serialization/Yaml.php
index 7abf366a97..3889dd36f4 100644
--- a/core/lib/Drupal/Component/Serialization/Yaml.php
+++ b/core/lib/Drupal/Component/Serialization/Yaml.php
@@ -2,29 +2,22 @@
 
 namespace Drupal\Component\Serialization;
 
-use Drupal\Core\StringTranslation\TranslationInterface;
-
 /**
  * Provides a YAML serialization implementation.
  *
  * Proxy implementation that will choose the best library based on availability.
  */
-class Yaml implements TranslatableSerializationInterface {
+class Yaml implements TaggedSerializationInterface {
+
+  use TaggedSerializationTrait;
 
   /**
    * The YAML implementation to use.
    *
-   * @var \Drupal\Component\Serialization\TranslatableSerializationInterface
+   * @var \Drupal\Component\Serialization\TaggedSerializationInterface
    */
   protected static $serializer;
 
-  /**
-   * The Translation Manager.
-   *
-   * @var \Drupal\Core\StringTranslation\TranslationInterface
-   */
-  protected static $translation;
-
   /**
    * {@inheritdoc}
    */
@@ -66,18 +59,13 @@ protected static function getSerializer() {
         // Otherwise, fallback to the Symfony implementation.
         static::$serializer = YamlSymfony::class;
       }
-      if (static::$translation) {
-        static::$serializer::setTranslation(static::$translation);
-      }
+      // Merge the tag callbacks from this proxy to the chosen serializer.
+      static::$serializer::setTagCallbacks(array_merge(
+        static::$serializer::getTagCallbacks(),
+        static::getTagCallbacks()
+      ));
     }
     return static::$serializer;
   }
 
-  /**
-   * {@inheritdoc}
-   */
-  public static function setTranslation(TranslationInterface $translation) {
-    static::$translation = $translation;
-  }
-
 }
diff --git a/core/lib/Drupal/Component/Serialization/YamlPecl.php b/core/lib/Drupal/Component/Serialization/YamlPecl.php
index 904422b468..651355b49b 100644
--- a/core/lib/Drupal/Component/Serialization/YamlPecl.php
+++ b/core/lib/Drupal/Component/Serialization/YamlPecl.php
@@ -7,11 +7,9 @@
 /**
  * Provides default serialization for YAML using the PECL extension.
  */
-class YamlPecl implements TranslatableSerializationInterface {
+class YamlPecl implements TaggedSerializationInterface {
 
-  use YamlTagMappingTrait {
-    getTagCallbacks as traitGetTagCallbacks;
-  }
+  use TaggedSerializationTrait;
 
   /**
    * {@inheritdoc}
@@ -85,9 +83,9 @@ public static function getFileExtension() {
    * {@inheritdoc}
    */
   public static function getTagCallbacks() {
-    $callbacks = static::traitGetTagCallbacks();
-    $callbacks[YAML_BOOL_TAG] = static::class . '::applyBooleanCallbacks';
-    return $callbacks;
+    return [
+      YAML_BOOL_TAG => static::class . '::applyBooleanCallbacks',
+    ];
   }
 
   /**
diff --git a/core/lib/Drupal/Component/Serialization/YamlSymfony.php b/core/lib/Drupal/Component/Serialization/YamlSymfony.php
index 7d864a8b6e..2ea01d4ba2 100644
--- a/core/lib/Drupal/Component/Serialization/YamlSymfony.php
+++ b/core/lib/Drupal/Component/Serialization/YamlSymfony.php
@@ -11,9 +11,9 @@
 /**
  * Default serialization for YAML using the Symfony component.
  */
-class YamlSymfony implements TranslatableSerializationInterface {
+class YamlSymfony implements TaggedSerializationInterface {
 
-  use YamlTagMappingTrait;
+  use TaggedSerializationTrait;
 
   /**
    * {@inheritdoc}
@@ -39,14 +39,22 @@ public static function decode($raw) {
       // 'foo: bar' with no newline will fail to parse otherwise.
       $data = $yaml->parse($raw, SymfonyYaml::PARSE_EXCEPTION_ON_INVALID_TYPE | SymfonyYaml::PARSE_CUSTOM_TAGS);
 
-      // Support tagged values.
+      $is_array = is_array($data);
+      if (!$is_array) {
+        $data = [$data];
+      }
+
+      // Support Symfony 3.3 TaggedValue objects.
       array_walk_recursive($data, function (&$value) {
         if ($value instanceof TaggedValue) {
-          $value = static::executeTagCallback('!' . $value->getTag(), (array) $value->getValue());
+          $callbacks = static::getTagCallbacks();
+          $args = (array) $value->getValue();
+          $tag = $value->getTag();
+          return isset($callbacks[$tag]) ? $callbacks[$tag](...$args) : $args;
         }
       });
 
-      return $data;
+      return $is_array ? $data : reset($data);
     }
     catch (\Exception $e) {
       throw new InvalidDataTypeException($e->getMessage(), $e->getCode(), $e);
diff --git a/core/lib/Drupal/Component/Serialization/YamlTagMappingTrait.php b/core/lib/Drupal/Component/Serialization/YamlTagMappingTrait.php
deleted file mode 100644
index 6c97f2c4d3..0000000000
--- a/core/lib/Drupal/Component/Serialization/YamlTagMappingTrait.php
+++ /dev/null
@@ -1,58 +0,0 @@
-<?php
-
-namespace Drupal\Component\Serialization;
-
-/**
- * Trait YamlTagMappingTrait.
- */
-trait YamlTagMappingTrait {
-
-  use TranslatableSerializationTrait;
-
-  /**
-   * Executes a callback for a tag with a specific value
-   *
-   * @param string $tag
-   *   The tag name.
-   * @param array $args
-   *   An array of arguments to pass to the callback.
-   *
-   * @return mixed
-   *   The callback result.
-   */
-  public static function executeTagCallback($tag, array $args) {
-    $callbacks = static::getTagCallbacks();
-    if (!isset($callbacks[$tag])) {
-      return $args;
-    }
-    $callback = $callbacks[$tag];
-    return $callback(...$args);
-  }
-
-  /**
-   * Retrieves a map of tag callbacks.
-   *
-   * @return array
-   *   An associative array where the key is the tag and the value is the
-   *   callback.
-   */
-  public static function getTagCallbacks() {
-    return [
-      '!translate' => static::class . '::applyTranslationCallback'
-    ];
-  }
-
-  /**
-   * Callback for applying the !translate tag.
-   *
-   * @param mixed ...$args
-   *   The arguments to pass to the Translation manager.
-   *
-   * @return \Drupal\Core\StringTranslation\TranslatableMarkup
-   *   A new TranslatableMarkup object.
-   */
-  public static function applyTranslationCallback(...$args) {
-    return static::getTranslation()->translate(...$args);
-  }
-
-}
diff --git a/core/lib/Drupal/Core/Serialization/Yaml.php b/core/lib/Drupal/Core/Serialization/Yaml.php
index 566f8cad4c..1b089249cf 100644
--- a/core/lib/Drupal/Core/Serialization/Yaml.php
+++ b/core/lib/Drupal/Core/Serialization/Yaml.php
@@ -2,6 +2,7 @@
 
 namespace Drupal\Core\Serialization;
 
+use Drupal\Component\Serialization\TaggedSerializationInterface;
 use Drupal\Core\Site\Settings;
 use Drupal\Component\Serialization\Yaml as ComponentYaml;
 
@@ -12,6 +13,13 @@
  */
 class Yaml extends ComponentYaml {
 
+  /**
+   * Translation Manager.
+   *
+   * @var \Drupal\Core\StringTranslation\TranslationInterface
+   */
+  protected static $translation;
+
   /**
    * {@inheritdoc}
    */
@@ -21,8 +29,51 @@ protected static function getSerializer() {
       $class = Settings::get('yaml_parser_class')) {
 
       static::$serializer = $class;
+
+      // Merge the tag callbacks from this proxy to the chosen serializer.
+      if (static::$serializer instanceof TaggedSerializationInterface) {
+        static::$serializer::setTagCallbacks(array_merge(
+          static::$serializer::getTagCallbacks(),
+          static::getTagCallbacks()
+        ));
+      }
     }
     return parent::getSerializer();
   }
 
+  /**
+   * Retrieves the Translation Manager.
+   *
+   * @return \Drupal\Core\StringTranslation\TranslationInterface
+   *   The Translation Manager.
+   */
+  protected static function getTranslation() {
+    if (!isset(static::$translation)) {
+      static::$translation = \Drupal::translation();
+    }
+    return static::$translation;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function getTagCallbacks() {
+    return [
+      '!translate' => static::class . '::applyTranslateCallback',
+    ];
+  }
+
+  /**
+   * Callback for applying the !translate tag.
+   *
+   * @param mixed ...
+   *   The arguments to pass to the Translation manager.
+   *
+   * @return \Drupal\Core\StringTranslation\TranslatableMarkup
+   *   A new TranslatableMarkup object.
+   */
+  public static function applyTranslateCallback(...$args) {
+    return static::getTranslation()->translate(...$args);
+  }
+
 }