diff -u b/core/modules/aggregator/src/Entity/Feed.php b/core/modules/aggregator/src/Entity/Feed.php
--- b/core/modules/aggregator/src/Entity/Feed.php
+++ b/core/modules/aggregator/src/Entity/Feed.php
@@ -226,7 +226,7 @@
 
     $fields['hash'] = BaseFieldDefinition::create('string')
       ->setLabel(t('Hash'))
-      ->setOption('is_alphanumeric', TRUE)
+      ->setSetting('is_alphanumeric', TRUE)
       ->setDescription(t('Calculated hash of the feed data, used for validating cache.'));
 
     $fields['etag'] = BaseFieldDefinition::create('string')
diff -u b/core/modules/file/src/Entity/File.php b/core/modules/file/src/Entity/File.php
--- b/core/modules/file/src/Entity/File.php
+++ b/core/modules/file/src/Entity/File.php
@@ -254,7 +254,7 @@
 
     $fields['filemime'] = BaseFieldDefinition::create('string')
       ->setLabel(t('File MIME type'))
-      ->setOption('is_alphanumeric', TRUE)
+      ->setSetting('is_alphanumeric', TRUE)
       ->setDescription(t("The file's MIME type."));
 
     $fields['filesize'] = BaseFieldDefinition::create('integer')