diff --git a/composer.json b/composer.json
index 2395575..4bffd79 100644
--- a/composer.json
+++ b/composer.json
@@ -18,6 +18,7 @@
     "require-dev": {
         "dealerdirect/phpcodesniffer-composer-installer": "^0.7.0",
         "drupal/coder": "^8.3",
-        "phpspec/prophecy-phpunit": "^2"
+        "phpspec/prophecy-phpunit": "^2",
+        "drupal/simple_sitemap": "^4.1"
     }
 }
diff --git a/helfi_proxy.info.yml b/helfi_proxy.info.yml
index c90ad0c..945fc10 100644
--- a/helfi_proxy.info.yml
+++ b/helfi_proxy.info.yml
@@ -6,3 +6,4 @@ core_version_requirement: ^8 || ^9
 dependencies:
   - path_alias
   - redirect
+  - drupal:helfi_api_base
diff --git a/helfi_proxy.module b/helfi_proxy.module
index fa91826..bdfa872 100644
--- a/helfi_proxy.module
+++ b/helfi_proxy.module
@@ -82,3 +82,29 @@ function helfi_proxy_page_attachments_alter(array &$attachments) {
     $attachments['#attached']['html_head'][] = [$helfi_content_type, $tag_name];
   }
 }
+
+/**
+ * Implements hook_page_attachments_alter().
+ */
+function helfi_proxy_simple_sitemap_links_alter(array &$links, $sitemap_variant) {
+  if ($sitemap_variant->getOriginalId() != 'default') {
+    return;
+  }
+
+  $userPreferredAdminLangcode = \drupal::currentUser()->getPreferredAdminLangcode(FALSE) ?: 'fi';
+
+  $config = \Drupal::configFactory()->get('simple_sitemap.settings')?->get('base_url');
+  if ($config) {
+    $pattern = "/\/$userPreferredAdminLangcode\/.*?\//";
+    foreach ($links as $key => &$link) {
+      $url = &$link['url'];
+      $link['url'] = preg_replace($pattern, '/', $url, 1);
+      $alternateUrls = &$link['alternate_urls'];
+      foreach ($alternateUrls as $alternateurl_key => $alternateUrl) {
+        $link['alternate_urls'][$alternateurl_key] = preg_replace($pattern, '/', $alternateUrl, 1);
+      }
+      $links[$key] = $link;
+    }
+  }
+
+}
diff --git a/src/Config/SitemapPathOverride.php b/src/Config/SitemapPathOverride.php
new file mode 100644
index 0000000..b8d7726
--- /dev/null
+++ b/src/Config/SitemapPathOverride.php
@@ -0,0 +1,78 @@
+<?php
+
+declare(strict_types = 1);
+
+namespace Drupal\helfi_proxy\Config;
+
+use Drupal\Core\Cache\CacheableMetadata;
+use Drupal\Core\Config\ConfigFactoryOverrideInterface;
+use Drupal\Core\Config\StorageInterface;
+use Drupal\Core\Http\RequestStack;
+use Drupal\Core\Language\LanguageManagerInterface;
+use Drupal\helfi_proxy\ActiveSitePrefix;
+
+/**
+ * Override sitemap path dynamically.
+ */
+class SitemapPathOverride implements ConfigFactoryOverrideInterface {
+
+  /**
+   * Constructs a new instance.
+   *
+   * @param \Drupal\helfi_proxy\ActiveSitePrefix $prefix
+   *   The active site prefix service.
+   * @param \Drupal\Core\Language\LanguageManagerInterface $languageManager
+   *   The language manager.
+   * @param \Drupal\Core\Http\RequestStack $requestStack
+   *   The request stack.
+   */
+  public function __construct(
+    private ActiveSitePrefix $prefix,
+    private LanguageManagerInterface $languageManager,
+    private RequestStack $requestStack,
+  ) {
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function loadOverrides($names): array {
+    $overrides = [];
+    $url = $this->requestStack->getCurrentRequest()?->getSchemeAndHttpHost();
+
+    if (!$url) {
+      return $overrides;
+    }
+
+    if (in_array('simple_sitemap.settings', $names)) {
+      $langcode = $this->languageManager->getCurrentLanguage()->getId();
+      $prefix = $this->prefix->getPrefix($langcode);
+      $baseUrl = sprintf('%s/%s/%s', $url, $langcode, $prefix);
+      $overrides['simple_sitemap.settings']['base_url'] = $baseUrl;
+    }
+
+    return $overrides;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getCacheSuffix() {
+    return 'SitemapPathOverride';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getCacheableMetadata($name) {
+    return new CacheableMetadata();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function createConfigObject($name, $collection = StorageInterface::DEFAULT_COLLECTION) {
+    return NULL;
+  }
+
+}
diff --git a/src/HelfiProxyServiceProvider.php b/src/HelfiProxyServiceProvider.php
index dc7a147..8d0d14b 100644
--- a/src/HelfiProxyServiceProvider.php
+++ b/src/HelfiProxyServiceProvider.php
@@ -6,6 +6,7 @@
 
 use Drupal\Core\DependencyInjection\ContainerBuilder;
 use Drupal\Core\DependencyInjection\ServiceProviderBase;
+use Drupal\helfi_proxy\Config\SitemapPathOverride;
 use Drupal\helfi_proxy\EventSubscriber\TunnistamoRedirectUrlSubscriber;
 use Symfony\Component\DependencyInjection\Reference;
 
@@ -29,6 +30,15 @@ public function register(ContainerBuilder $container) {
         ->addArgument(new Reference('helfi_proxy.proxy_manager'))
         ->addArgument(new Reference('helfi_proxy.active_prefix'));
     }
+
+    if (isset($modules['simple_sitemap'])) {
+      $container->register('helfi_proxy.sitemap_path_override', SitemapPathOverride::class)
+        ->addTag('config.factory.override')
+        ->addArgument(new Reference('helfi_proxy.active_prefix'))
+        ->addArgument(new Reference('language_manager'))
+        ->addArgument(new Reference('request_stack'));
+    }
+
   }
 
 }