--- /dev/null
+<?php
+// @codingStandardsIgnoreFile
+
+use Drupal\Core\Database\Database;
+
+$connection = Database::getConnection();
+
+// Simulate an entity type that had previously set an initial key schema for a
+// field.
+$schema = $connection->select('key_value')
+ ->fields('key_value', ['value'])
+ ->condition('collection', 'entity.storage_schema.sql')
+ ->condition('name', 'entity_test_update.field_schema_data.name')
+ ->execute()
+ ->fetchField();
+
+$schema = unserialize($schema);
+$schema['entity_test_update']['fields']['name']['initial'] = 'test';
+
+$connection->update('key_value')
+ ->fields(['value' => serialize($schema)])
+ ->condition('collection', 'entity.storage_schema.sql')
+ ->condition('name', 'entity_test_update.field_schema_data.name')
+ ->execute();