diff -u b/core/lib/Drupal/Core/TypedData/Plugin/DataType/Map.php b/core/lib/Drupal/Core/TypedData/Plugin/DataType/Map.php
--- b/core/lib/Drupal/Core/TypedData/Plugin/DataType/Map.php
+++ b/core/lib/Drupal/Core/TypedData/Plugin/DataType/Map.php
@@ -157,22 +157,29 @@
    */
   public function getProperties($include_computed = FALSE) {
     $properties = [];
+    $property_definitions = $this->definition->getPropertyDefinitions();
+    if (!empty($property_definitions)) {
+      foreach ($property_definitions as $name => $definition) {
+        if ($include_computed || !$definition->isComputed()) {
+          $properties[$name] = $this->get($name);
+        }
+      }
+    }
     // If module creator send an array to map dataType and don't define setPropertyDefinition,
     // Auto creating the PropertyDefinition so that it can   be normalized
-    $property_definitions = $this->definition->getPropertyDefinitions();
-    if (empty($property_definitions) && get_class($this->getDataDefinition()) == 'Drupal\Core\TypedData\MapDataDefinition') {
-      $values = $this->getValue();
+    elseif (get_class($this->getDataDefinition()) == 'Drupal\Core\TypedData\MapDataDefinition') {
+      $values = $this->values;
       if (is_array($values)) {
         foreach ($values as $key => $value) {
           if (!empty($value) && is_array($value)) {
-            $data = \Drupal::typedDataManager()->create(
+            $properties[$key] = \Drupal::typedDataManager()->create(
               MapDataDefinition::create(),
               $value,
               $key
             );
           }
           else {
-            $data = \Drupal::typedDataManager()->create(
+            $properties[$key] = \Drupal::typedDataManager()->create(
             // Give array's value a DataType,So that drupal can find which normalizer to be used to normalize it
             // Because we don't know the type of the value,so we use 'any',
             // If you don't want to use 'any',Please define it by yourself use setPropertyDefinition
@@ -181,13 +188,7 @@
               $key
             );
           }
-          $this->definition->setPropertyDefinition($key, $data->getDataDefinition());
-        }
-      }
-    }
-    foreach ($this->definition->getPropertyDefinitions() as $name => $definition) {
-      if ($include_computed || !$definition->isComputed()) {
-        $properties[$name] = $this->get($name);
+        };
       }
     }
 
diff -u b/core/tests/Drupal/Tests/Core/TypedData/MapDataNormalizeTest.php b/core/tests/Drupal/Tests/Core/TypedData/MapDataNormalizeTest.php
--- b/core/tests/Drupal/Tests/Core/TypedData/MapDataNormalizeTest.php
+++ b/core/tests/Drupal/Tests/Core/TypedData/MapDataNormalizeTest.php
@@ -34,7 +34,6 @@
     parent::setUp();
     $this->serializer = \Drupal::service('serializer');
     $this->typedDataManager = \Drupal::typedDataManager();
-
   }
 
   /**