diff --git a/classes/helpers.php b/classes/helpers.php
index 5f7bcdf..95da1c1 100644
--- a/classes/helpers.php
+++ b/classes/helpers.php
@@ -95,8 +95,29 @@ public static function get_option_page_ids() {
 	 * @return bool
 	 */
 	public static function already_localized( $post_id ) {
-		preg_match( '/[a-z]{2}_[A-Z]{2}/', $post_id, $language );
+		$locales_regex_fragment = self::locales_regex_fragment();
+		if ( ! $locales_regex_fragment ) {
+			return false;
+		}
+		preg_match( '/_(' . $locales_regex_fragment . ')$/', $post_id, $language );
 
 		return ! empty( $language );
 	}
+
+	/**
+	 * @return string A regex fragment for all polylang configured locales
+	 */
+	public static function locales_regex_fragment(): string {
+		$locales = pll_languages_list( [ 'hide_empty' => false, 'fields' => 'locale' ] );
+		if ( ! $locales ) {
+			return '';
+		}
+
+		return sprintf(
+			'(%s)',
+			implode( '|', array_map( function ( $lang ) {
+				return preg_quote( $lang, '/' );
+			}, $locales ) )
+		);
+	}
 }
diff --git a/classes/main.php b/classes/main.php
index b2638fb..f5b992a 100644
--- a/classes/main.php
+++ b/classes/main.php
@@ -51,11 +51,15 @@ public function get_default_reference( $reference, $field_name, $post_id ) {
 			return $reference;
 		}
 
+		if ( ! $locales_regex_fragment = Helpers::locales_regex_fragment() ) {
+			return $reference;
+		}
+
 		/**
 		 * Dynamically get the options page ID
 		 * @see : https://regex101.com/r/58uhKg/2/
 		 */
-		$_post_id = preg_replace( '/(_[a-z]{2}_[A-Z]{2})/', '', $post_id );
+		$_post_id = preg_replace( '/(_' . $locales_regex_fragment . ')$/', '', $post_id );
 
 		remove_filter( 'acf/load_reference', [ $this, 'get_default_reference' ] );
 		$reference = acf_get_reference( $field_name, $_post_id );
@@ -85,8 +89,8 @@ public function get_default_value( $value, $post_id, $field ) {
 		/**
 		 * Activate or deactivate the default value (all languages) for the given post id
 		 *
-		 * @param bool $show_default : whatever to show default for the given post id
-		 * @param string $original_post_id : the original post id without lang attributes
+		 * @param  bool  $show_default  : whatever to show default for the given post id
+		 * @param  string  $original_post_id  : the original post id without lang attributes
 		 *
 		 * @since 1.0.4
 		 */
@@ -144,8 +148,8 @@ function ( $value_c ) {
 	/**
 	 * Manage to change the post_id with the current lang to save option against
 	 *
-	 * @param string $future_post_id
-	 * @param string $original_post_id
+	 * @param  string  $future_post_id
+	 * @param  string  $original_post_id
 	 *
 	 * @return string
 	 * @author Maxime CULEA