diff --git a/cake/libs/cake_session.php b/cake/libs/cake_session.php
index 0acedace6..f84315215 100644
--- a/cake/libs/cake_session.php
+++ b/cake/libs/cake_session.php
@@ -239,7 +239,7 @@ class CakeSession {
 		self::_startSession();
 		$started = self::started();
 
-		if (!self::id() && $started) {
+		if (self::id() && $started) {
 			self::_checkValid();
 		}
 
@@ -492,12 +492,11 @@ class CakeSession {
  * @return void
  */
 	public static function destroy() {
-		$_SESSION = array();
+		$_SESSION = null;
 		self::$id = null;
 		self::init(self::$path);
 		self::start();
 		self::renew();
-		self::_checkValid();
 	}
 
 /**
diff --git a/cake/tests/cases/libs/cake_session.test.php b/cake/tests/cases/libs/cake_session.test.php
index c9307b07b..e0c21881e 100644
--- a/cake/tests/cases/libs/cake_session.test.php
+++ b/cake/tests/cases/libs/cake_session.test.php
@@ -111,7 +111,7 @@ class CakeSessionTest extends CakeTestCase {
  * @return void
  */
 	function testSessionConfigIniSetting() {
-		$_SESSION = array();
+		$_SESSION = null;
 		session_destroy();
 
 		Configure::write('Session', array(
@@ -188,6 +188,34 @@ class CakeSessionTest extends CakeTestCase {
 		$this->assertEqual('cakephp.org', TestCakeSession::$host);
 	}
 
+/**
+ * test valid with bogus user agent.
+ *
+ * @return void
+ */
+	function testValidBogusUserAgent() {
+		Configure::write('Session.checkAgent', true);
+		TestCakeSession::start();
+		$this->assertTrue(TestCakeSession::valid(), 'Newly started session should be valid');
+
+		TestCakeSession::userAgent('bogus!');
+		$this->assertFalse(TestCakeSession::valid(), 'user agent mismatch should fail.');
+	}
+
+/**
+ * test valid with bogus user agent.
+ *
+ * @return void
+ */
+	function testValidTimeExpiry() {
+		Configure::write('Session.checkAgent', true);
+		TestCakeSession::start();
+		$this->assertTrue(TestCakeSession::valid(), 'Newly started session should be valid');
+
+		TestCakeSession::$time = strtotime('next year');
+		$this->assertFalse(TestCakeSession::valid(), 'time should cause failure.');
+	}
+
 /**
  * testCheck method
  *
@@ -299,6 +327,7 @@ class CakeSessionTest extends CakeTestCase {
 		$_SESSION = null;
 		$this->assertFalse(TestCakeSession::started());
 		$this->assertTrue(TestCakeSession::start());
+		$this->assertTrue(TestCakeSession::started());
 	}
 
 /**