diff --git a/core/modules/serialization/src/Normalizer/MapNormalizer.php b/core/modules/serialization/src/Normalizer/MapNormalizer.php
index 115bb64ffb..1bbe4290b1 100644
--- a/core/modules/serialization/src/Normalizer/MapNormalizer.php
+++ b/core/modules/serialization/src/Normalizer/MapNormalizer.php
@@ -24,7 +24,7 @@ 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($definition->g())) {
+      if ($definition instanceof ComplexDataDefinitionInterface && empty($definition->getPropertyDefinitions())) {
         return TRUE;
       }
     }