diff --git a/src/wp-includes/fonts/class-wp-font-utils.php b/src/wp-includes/fonts/class-wp-font-utils.php
index 5bca536d2d..22baff3a5a 100644
--- a/src/wp-includes/fonts/class-wp-font-utils.php
+++ b/src/wp-includes/fonts/class-wp-font-utils.php
@@ -132,7 +132,7 @@ class WP_Font_Utils {
 			$slug_elements
 		);
 
-		return sanitize_text_field( join( ';', $slug_elements ) );
+		return sanitize_text_field( implode( ';', $slug_elements ) );
 	}
 
 	/**