diff --git a/src/wp-includes/functions.php b/src/wp-includes/functions.php
index 088fe9d07f..658afaad3c 100644
--- a/src/wp-includes/functions.php
+++ b/src/wp-includes/functions.php
@@ -4349,10 +4349,11 @@ function smilies_init() {
  * @since 2.3.0 `$args` can now also be an object.
  *
  * @param string|array|object $args     Value to merge with $defaults.
- * @param array               $defaults Optional. Array that serves as the defaults. Default empty.
+ * @param array               $defaults Optional. Array that serves as the defaults.
+ *                                      Default empty array.
  * @return array Merged user defined values with defaults.
  */
-function wp_parse_args( $args, $defaults = '' ) {
+function wp_parse_args( $args, $defaults = array() ) {
 	if ( is_object( $args ) ) {
 		$parsed_args = get_object_vars( $args );
 	} elseif ( is_array( $args ) ) {
@@ -4361,7 +4362,7 @@ function wp_parse_args( $args, $defaults = '' ) {
 		wp_parse_str( $args, $parsed_args );
 	}
 
-	if ( is_array( $defaults ) ) {
+	if ( is_array( $defaults ) && $defaults ) {
 		return array_merge( $defaults, $parsed_args );
 	}
 	return $parsed_args;