diff --git a/wp-includes/functions.php b/wp-includes/functions.php
index fbe1219866..42f6873b64 100644
--- a/wp-includes/functions.php
+++ b/wp-includes/functions.php
@@ -782,7 +782,7 @@ function add_query_arg() {
 	$qs = urlencode_deep( $qs ); // this re-URL-encodes things that were already in the query string
 	if ( is_array( $args[0] ) ) {
 		$kayvees = $args[0];
-		$qs = array_merge( $qs, $kayvees );
+		$qs = array_replace( $qs, $kayvees );
 	} else {
 		$qs[ $args[0] ] = $args[1];
 	}
diff --git a/wp-includes/version.php b/wp-includes/version.php
index c45d6c3a6a..b9e6605b4f 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.2-beta3-31965';
+$wp_version = '4.2-beta3-31966';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.