diff --git a/src/CustomPostType.php b/src/CustomPostType.php
index ea44cf0..a23e0fc 100644
--- a/src/CustomPostType.php
+++ b/src/CustomPostType.php
@@ -193,7 +193,7 @@ function addMetaFields(array $metaFields): self {
 
 	function addMetaField(string $metaKey, array $args): self {
 
-		MetaFields::instance()->addPostMeta($this->postType, $metaKey, $args);
+		mf()->addPostMeta($this->postType, $metaKey, $args);
 
 		return $this;
 	}
diff --git a/src/functions.php b/src/functions.php
index 4265850..424c688 100644
--- a/src/functions.php
+++ b/src/functions.php
@@ -16,17 +16,17 @@ function mf() {
 
 if (!function_exists('getVisitorCountryCode')) {
 	function getVisitorCountryCode(): string {
-		return strtoupper(apply_filters('visitor_country_code', ''));
+		return strtoupper(apply_filters('visitor_country_code', null));
 	}
 }
 
-add_filter('user_country_code', 'layered_visitor_country_code_woocommerce');
-add_filter('user_country_code', 'layered_visitor_country_code_headers');
+add_filter('visitor_country_code', 'layeredUserCountryCodeWooCommerce');
+add_filter('visitor_country_code', 'layeredUserCountryCodeHeaders');
 
-function layered_visitor_country_code_woocommerce(string $countryCode = ''): string {
+function layeredUserCountryCodeWooCommerce(string $countryCode = null): ?string {
 	if (empty($countryCode) && class_exists('WC_Geolocation')) {
 		$location = WC_Geolocation::geolocate_ip();
-		if ($location['country'] && !in_array($location['country'], array('A1', 'A2', 'EU', 'AP'))) {
+		if ($location['country'] && !in_array($location['country'], ['A1', 'A2', 'EU', 'AP'])) {
 			$countryCode = $location['country'];
 		}
 	}
@@ -34,7 +34,7 @@ function layered_visitor_country_code_woocommerce(string $countryCode = ''): str
 	return $countryCode;
 }
 
-function if_menu_user_country_code_headers(string $countryCode = ''): string {
+function layeredUserCountryCodeHeaders(string $countryCode = null): ?string {
 	if (empty($countryCode)) {
 		foreach (['HTTP_CF_IPCOUNTRY', 'X-AppEngine-country', 'CloudFront-Viewer-Country', 'GEOIP_COUNTRY_CODE', 'HTTP_X_COUNTRY_CODE', 'HTTP_X_GEO_COUNTRY'] as $key) {
 			if (isset($_SERVER[$key]) && $_SERVER[$key] && !in_array($_SERVER[$key], ['XX', 'ZZ', 'A1', 'A2', 'EU', 'AP'])) {