diff --git a/tests/phpunit/includes/speed-trap-listener.php b/tests/phpunit/includes/speed-trap-listener.php
index 5f79f43094..a0000eed03 100644
--- a/tests/phpunit/includes/speed-trap-listener.php
+++ b/tests/phpunit/includes/speed-trap-listener.php
@@ -59,6 +59,18 @@ class SpeedTrapListener implements PHPUnit_Framework_TestListener
     {
     }
 
+    /**
+     * A warning occurred.
+     *
+     * @param PHPUnit_Framework_Test    $test
+     * @param PHPUnit_Framework_Warning $e
+     * @param float                     $time
+     * @since Method available since Release 5.1.0
+     */
+    public function addWarning(PHPUnit_Framework_Test $test, PHPUnit_Framework_Warning $e, $time)
+    {
+    }
+
     /**
      * A failure occurred.
      *