diff --git a/core/lib/Drupal/Core/TypedData/Plugin/DataType/Map.php b/core/lib/Drupal/Core/TypedData/Plugin/DataType/Map.php
index 5d1de528e7..a95c14b30e 100644
--- a/core/lib/Drupal/Core/TypedData/Plugin/DataType/Map.php
+++ b/core/lib/Drupal/Core/TypedData/Plugin/DataType/Map.php
@@ -2,8 +2,6 @@
 
 namespace Drupal\Core\TypedData\Plugin\DataType;
 
-use Drupal\Core\TypedData\DataDefinition;
-use Drupal\Core\TypedData\MapDataDefinition;
 use Drupal\Core\TypedData\TypedData;
 use Drupal\Core\TypedData\ComplexDataInterface;
 
@@ -162,33 +160,6 @@ public function getProperties($include_computed = FALSE) {
         $properties[$name] = $this->get($name);
       }
     }
-
-    // In case someone uses the Map data type or the MapItem field type,
-    // $this->definition->getPropertyDefinitions() is empty, as these maps meant to have different
-    // values per entity.
-    // Instead iterate over the values to define properties on the fly. By doing so normalization
-    // will work automatically.
-    if (empty($properties) && $this->getDataDefinition() instanceof MapDataDefinition) {
-      foreach ($this->values as $key => $value) {
-        if (!empty($value) && is_array($value)) {
-          // Recursively create the data definition for each element of the child array.
-          $properties[$key] = $this->getTypedDataManager()->create(
-            MapDataDefinition::create(),
-            $value,
-            $key
-          );
-        }
-        else {
-          $properties[$key] = $this->getTypedDataManager()->create(
-          // For scalar values we use 'any' as we don't have more information about it.
-          // If you have more information about your properties, please use setPropertyDefinition.
-            DataDefinition::create('any'),
-            $value,
-            $key
-          );
-        }
-      }
-    }
     return $properties;
   }
 
diff --git a/core/modules/serialization/serialization.services.yml b/core/modules/serialization/serialization.services.yml
index dca6094787..1e28a28b2c 100644
--- a/core/modules/serialization/serialization.services.yml
+++ b/core/modules/serialization/serialization.services.yml
@@ -71,6 +71,10 @@ services:
     class: Drupal\serialization\Normalizer\TypedDataNormalizer
     tags:
       - { name: normalizer }
+  serializer.normalizer.map:
+    class: Drupal\serialization\Normalizer\MapNormalizer
+    tags:
+      - { name: normalizer, priority: 25}
   serializer.encoder.json:
     class: Drupal\serialization\Encoder\JsonEncoder
     tags:
diff --git a/core/modules/serialization/src/Normalizer/MapNormalizer.php b/core/modules/serialization/src/Normalizer/MapNormalizer.php
new file mode 100644
index 0000000000..115bb64ffb
--- /dev/null
+++ b/core/modules/serialization/src/Normalizer/MapNormalizer.php
@@ -0,0 +1,34 @@
+<?php
+
+namespace Drupal\serialization\Normalizer;
+
+use Drupal\Core\TypedData\ComplexDataDefinitionInterface;
+
+/**
+ * Converts Map objects into arrays.
+ *
+ * This normalizer only supports Map objects that do not have have property
+ * definitions.
+ */
+class MapNormalizer extends TypedDataNormalizer {
+
+  /**
+   * {@inheritdoc}
+   */
+  protected $supportedInterfaceOrClass = '\Drupal\Core\TypedData\Plugin\DataType\Map';
+
+  /**
+   * {@inheritdoc}
+   */
+  public function supportsNormalization($data, $format = NULL) {
+    /* @var \Drupal\Core\TypedData\Plugin\DataType\Map $data  */
+    if (parent::supportsNormalization($data, $format)) {
+      $definition = $data->getDataDefinition();
+      if ($definition instanceof ComplexDataDefinitionInterface && empty($definition->g())) {
+        return TRUE;
+      }
+    }
+    return FALSE;
+  }
+
+}