diff --git a/mkdocs_git_revision_date_localized_plugin/plugin.py b/mkdocs_git_revision_date_localized_plugin/plugin.py
index 60ab798..afc09ae 100644
--- a/mkdocs_git_revision_date_localized_plugin/plugin.py
+++ b/mkdocs_git_revision_date_localized_plugin/plugin.py
@@ -79,7 +79,7 @@ def on_config(self, config: config_options.Config, **kwargs) -> Dict[str, Any]:
         # theme locale
         if "theme" in config and "locale" in config.get("theme"):
             custom_theme = config.get("theme")
-            theme_locale = custom_theme._vars.get("locale")
+            theme_locale = custom_theme.locale
             logging.debug(
                 "Locale '%s' extracted from the custom theme: '%s'"
                 % (theme_locale, custom_theme.name)