diff --git a/core/lib/Drupal/Core/Entity/EntityStorageBase.php b/core/lib/Drupal/Core/Entity/EntityStorageBase.php
index a6ba4084ae..1d956f551f 100644
--- a/core/lib/Drupal/Core/Entity/EntityStorageBase.php
+++ b/core/lib/Drupal/Core/Entity/EntityStorageBase.php
@@ -108,8 +108,8 @@ public function __construct(EntityTypeInterface $entity_type, MemoryCacheInterfa
    * Retrieves the class name used to create the entity.
    *
    * @param string $bundle
-   *   A specific entity type bundle identifier. Note: depending on how the
-   *   entity is configured, a bundle may not be provided.
+   *   (optional) A specific entity type bundle identifier. Can be omitted in
+   *   the case of entity types without bundles, like User.
    *
    * @return string
    *   A class name.
@@ -364,16 +364,7 @@ protected function preLoad(array &$ids = NULL) {
    *   Associative array of query results, keyed on the entity ID.
    */
   protected function postLoad(array &$entities) {
-    $entity_classes = [];
-
-    /** @var \Drupal\Core\Entity\EntityInterface $entity */
-    foreach ($entities as $id => &$entity) {
-      $entity_class = get_class($entity);
-      if (!isset($entity_classes[$entity_class])) {
-        $entity_classes[$entity_class] = [];
-      }
-      $entity_classes[$entity_class][$id] = &$entity;
-    }
+    $entity_classes = $this->getEntityClasses($entities);
 
     foreach ($entity_classes as $entity_class => &$items) {
       $entity_class::postLoad($this, $entities);
@@ -405,6 +396,7 @@ protected function mapFromStorageRecords(array $records) {
     $entities = [];
     foreach ($records as $record) {
       $entity_class = $this->getEntityClass();
+      /* @var $entity \Drupal\Core\Entity\EntityInterface */
       $entity = new $entity_class($record, $this->entityTypeId);
       $entities[$entity->id()] = $entity;
     }
@@ -420,6 +412,7 @@ protected function mapFromStorageRecords(array $records) {
    *   The entity being saved.
    *
    * @return bool
+   *   TRUE if this entity exists in storage, FALSE otherwise.
    */
   abstract protected function has($id, EntityInterface $entity);
 
@@ -438,16 +431,7 @@ public function delete(array $entities) {
       $keyed_entities[$entity->id()] = $entity;
     }
 
-    $entity_classes = [];
-
-    /** @var \Drupal\Core\Entity\EntityInterface $entity */
-    foreach ($keyed_entities as $id => $entity) {
-      $entity_class = get_class($entity);
-      if (!isset($entity_classes[$entity_class])) {
-        $entity_classes[$entity_class] = [];
-      }
-      $entity_classes[$entity_class][$id] = $entity;
-    }
+    $entity_classes = $this->getEntityClasses($keyed_entities);
 
     // Allow code to run before deleting.
     foreach ($entity_classes as $entity_class => &$items) {
@@ -650,4 +634,27 @@ public function getAggregateQuery($conjunction = 'AND') {
    */
   abstract protected function getQueryServiceName();
 
+  /**
+   * Return an array of entities indexed by class name and ID.
+   *
+   * @param \Drupal\Core\Entity\EntityInterface[] $entities
+   *   The array of entities to index.
+   *
+   * @return array
+   *   An array of the passed-in entities, indexed by their class name and ID.
+   */
+  protected function getEntityClasses(array $entities) {
+    $entity_classes = [];
+
+    foreach ($entities as $id => &$entity) {
+      $entity_class = get_class($entity);
+      if (!isset($entity_classes[$entity_class])) {
+        $entity_classes[$entity_class] = [];
+      }
+      $entity_classes[$entity_class][$id] = &$entity;
+    }
+
+    return $entity_classes;
+  }
+
 }
diff --git a/core/lib/Drupal/Core/Entity/EntityTypeRepository.php b/core/lib/Drupal/Core/Entity/EntityTypeRepository.php
index 97d4ab2c7d..bfd25b6f82 100644
--- a/core/lib/Drupal/Core/Entity/EntityTypeRepository.php
+++ b/core/lib/Drupal/Core/Entity/EntityTypeRepository.php
@@ -78,46 +78,112 @@ public function getEntityTypeFromClass($class_name) {
       return $this->classNameEntityTypeMap[$class_name];
     }
 
+    if ($entity_type_id = $this->getExactEntityTypeFromClass($class_name)) {
+      $this->classNameEntityTypeMap[$class_name] = $entity_type_id;
+      return $entity_type_id;
+    }
+
+    throw new NoCorrespondingEntityClassException($class_name);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function clearCachedDefinitions() {
+    $this->classNameEntityTypeMap = [];
+  }
+
+  /**
+   * Return the matching entity type ID if there is one.
+   *
+   * @param string $class_name
+   *   The fully-qualified class name to look up.
+   *
+   * @return string|null
+   *   The entity type ID, or NULL if one does not exist.
+   */
+  protected function getExactEntityTypeFromClass($class_name) {
     $same_class = 0;
+
+    // Even if an exact match is returned, we need to check if a subclass is
+    // also defined so we can throw an AmbiguousEntityClassException.
+    $exact = $this->getEntityTypeFromExactClass($class_name, $same_class);
+    $subclass = $this->getEntityTypeFromSubclass($class_name, $same_class);
+
+    return $exact ?: $subclass;
+  }
+
+  /**
+   * Get the entity type ID, if an exact class name match exists.
+   *
+   * @param string $class_name
+   *   The fully-qualified class name to look up.
+   * @param int &$same_class
+   *   A counter to keep track of if multiple classes implement the same entity
+   *   type.
+   *
+   * @return string|null
+   *   The entity type ID, or NULL if one does not exist.
+   */
+  protected function getEntityTypeFromExactClass($class_name, &$same_class) {
     $entity_type_id = NULL;
     $definitions = $this->entityTypeManager->getDefinitions();
 
     // Attempt to find an exact entity class name match.
     foreach ($definitions as $entity_type) {
       if ($class_name === $entity_type->getClass() || $class_name === $entity_type->getOriginalClass()) {
-        $entity_type_id = $entity_type->id();
-        if ($same_class++) {
-          throw new AmbiguousEntityClassException($class_name);
-        }
+        $entity_type_id = $this->getUnambiguousEntityType($class_name, $same_class, $entity_type);
       }
     }
+    return $entity_type_id;
+  }
 
-    // Attempt to find a subclassed entity class name match.
-    if (!$entity_type_id) {
-      foreach ($definitions as $entity_type) {
-        if (is_subclass_of($class_name, $entity_type->getClass()) || is_subclass_of($class_name, $entity_type->getOriginalClass())) {
-          $entity_type_id = $entity_type->id();
-          if ($same_class++) {
-            throw new AmbiguousEntityClassException($class_name);
-          }
-        }
+  /**
+   * Get the entity type ID, if a subclass exists.
+   *
+   * @param string $class_name
+   *   The fully-qualified class name to look up.
+   * @param int &$same_class
+   *   A counter to keep track of if multiple classes implement the same entity
+   *   type.
+   *
+   * @return string|null
+   *   The entity type ID, or NULL if one does not exist.
+   */
+  protected function getEntityTypeFromSubclass($class_name, int &$same_class) {
+    $definitions = $this->entityTypeManager->getDefinitions();
+    $entity_type_id = NULL;
+    foreach ($definitions as $entity_type) {
+      if (is_subclass_of($class_name, $entity_type->getClass()) || is_subclass_of($class_name, $entity_type->getOriginalClass())) {
+        $entity_type_id = $this->getUnambiguousEntityType($class_name, $same_class, $entity_type);
       }
     }
-
-    // Return the matching entity type ID if there is one.
-    if ($entity_type_id) {
-      $this->classNameEntityTypeMap[$class_name] = $entity_type_id;
-      return $entity_type_id;
-    }
-
-    throw new NoCorrespondingEntityClassException($class_name);
+    return $entity_type_id;
   }
 
   /**
-   * {@inheritdoc}
+   * Get the entity type ID, ensuring only a single class implements the bundle.
+   *
+   * @param string $class_name
+   *   The fully-qualified class name to look up.
+   * @param int &$same_class
+   *   A counter to keep track of if multiple classes implement the same entity
+   *   type.
+   * @param \Drupal\Core\Entity\EntityTypeInterface $entity_type
+   *   The entity type corresponding to the class name.
+   *
+   * @return string
+   *   The entity type ID.
+   *
+   * @throws \Drupal\Core\Entity\Exception\AmbiguousEntityClassException
+   *   Thrown if multiple classes implement the same entity type and bundle.
    */
-  public function clearCachedDefinitions() {
-    $this->classNameEntityTypeMap = [];
+  private function getUnambiguousEntityType($class_name, int &$same_class, EntityTypeInterface $entity_type) {
+    if ($same_class++) {
+      throw new AmbiguousEntityClassException($class_name);
+    }
+
+    return $entity_type->id();
   }
 
 }