public function addFallbackLocale($locale, $preinit = false) {
		$locale = (string) $locale;
		$locale = $this->normalizeLocale($locale);
		
		if (in_array($locale, $this->fallbackLocales, true)) {
			return $this;
		}
		
		$this->fallbackLocales[] = $locale;
		
		if ($preinit) {
			$this->addPreinitLocale($locale);
		}
		
		return $this;
	}