diff --git a/WebDriver/Driver.php b/WebDriver/Driver.php
index 2fe6c84..d049dfe 100644
--- a/WebDriver/Driver.php
+++ b/WebDriver/Driver.php
@@ -371,6 +371,8 @@ public function activate_ime() {
   public function select_frame($identifier = null) {
     if ($identifier !== null) {
       $this->get_element($identifier); // POST /session/:sessionId/frame does not use implicit wait but POST /session/:sessionId/element does
+      $locator = WebDriver::ParseLocator($identifier);
+      $identifier = $locator['value'];
     }
     $payload = array("id" => $identifier);
     $this->execute("POST", "/session/:sessionId/frame", $payload);