diff --git a/email_registration.module b/email_registration.module
index 71095c2..e9992d8 100644
--- a/email_registration.module
+++ b/email_registration.module
@@ -54,6 +54,59 @@ function email_registration_user_insert(UserInterface $account) {
 }
 
 /**
+ * Implements hook_ENTITY_TYPE_presave().
+ */
+function email_registration_user_presave(UserInterface $account) {
+  // Don't do anything for a new account: hook_ENTITY_TYPE_insert() handles
+  // this.
+  if (!$account->id()) {
+    return;
+  }
+
+  // Don't do anything if the account email hasn't changed.
+  if ($account->getEmail() == $account->original->getEmail()) {
+    return;
+  }
+
+  // Don't do anything if the account name is set to the randomly generated
+  // string that we set on account creation.
+  $name = $account->getAccountName();
+  if (!empty($name) && strpos($name, 'email_registration_') === 0) {
+    return;
+  }
+
+  // Other modules may implement hook_email_registration_name($edit, $account)
+  // to generate a username (return a string to be used as the username, NULL
+  // to have email_registration generate it).
+  $names = Drupal::moduleHandler()->invokeAll('email_registration_name', [$account]);
+  // Remove any empty entries.
+  $names = array_filter($names);
+
+  if (empty($names)) {
+    // Strip off everything after the @ sign.
+    $new_name = preg_replace('/@.*$/', '', $account->getEmail());
+    // Clean up the username.
+    $new_name = email_registration_cleanup_username($new_name);
+  }
+  else {
+    // One would expect a single implementation of the hook, but if there
+    // are multiples out there use the last one.
+    $new_name = array_pop($names);
+  }
+
+  // Ensure whatever name we have is unique.
+  $new_name = email_registration_unique_username($new_name, $account->id());
+
+  $account->setUsername($new_name);
+  if ($account->isValidationRequired() && !$account->validate()) {
+    \Drupal::logger('email_registration')->error('Email registration failed setting the new name on user @id.', ['@id' => $account->id()]);
+
+    // Restore the old user name.
+    $account->setUsername($account->original->getAccountName());
+  }
+}
+
+/**
  * Makes the username unique.
  *
  * Given a starting point for a Drupal username (e.g. the name portion of an