diff --git a/core/lib/Drupal/Core/Entity/ContentEntityBase.php b/core/lib/Drupal/Core/Entity/ContentEntityBase.php
index b4f43db..d56eaaf 100644
--- a/core/lib/Drupal/Core/Entity/ContentEntityBase.php
+++ b/core/lib/Drupal/Core/Entity/ContentEntityBase.php
@@ -780,7 +780,7 @@ public function &__get($name) {
     if (isset($this->fields[$name][$this->activeLangcode])) {
       return $this->fields[$name][$this->activeLangcode];
     }
-    // Inline getFieldDefinition() to speed up things.
+    // Inline getFieldDefinition() to speed things up.
     if (!isset($this->fieldDefinitions)) {
       $this->getFieldDefinitions();
     }
@@ -802,8 +802,12 @@ public function &__get($name) {
    * Uses default language always.
    */
   public function __set($name, $value) {
+    // Inline getFieldDefinition() to speed things up.
+    if (!isset($this->fieldDefinitions)) {
+      $this->getFieldDefinitions();
+    }
     // Handle Field API fields.
-    if ($this->hasField($name)) {
+    if (isset($this->fieldDefinitions[$name])) {
       // Support setting values via property objects.
       if ($value instanceof TypedDataInterface && !$value instanceof EntityInterface) {
         $value = $value->getValue();