diff --git a/application/Utils.php b/application/Utils.php
index cb03f11c7..aa5cc193d 100755
--- a/application/Utils.php
+++ b/application/Utils.php
@@ -156,7 +156,7 @@ function is_session_id_valid($sessionId)
         return false;
     }
 
-    if (!preg_match('/^[a-z0-9]{2,32}$/i', $sessionId)) {
+    if (!preg_match('/^[-,a-z0-9]{1,128}$/i', $sessionId)) {
         return false;
     }
 
diff --git a/index.php b/index.php
index d615da1f5..e0a389cb3 100755
--- a/index.php
+++ b/index.php
@@ -92,16 +92,18 @@
 // Prevent PHP form using sessionID in URL if cookies are disabled.
 ini_set('session.use_trans_sid', false);
 
-// Regenerate session id if invalid or not defined in cookie.
-if (isset($_COOKIE['shaarli']) && !is_session_id_valid($_COOKIE['shaarli'])) {
-    $_COOKIE['shaarli'] = uniqid();
-}
 session_name('shaarli');
 // Start session if needed (Some server auto-start sessions).
 if (session_id() == '') {
     session_start();
 }
 
+// Regenerate session id if invalid or not defined in cookie.
+if (isset($_COOKIE['shaarli']) && !is_session_id_valid($_COOKIE['shaarli'])) {
+    session_regenerate_id(true);
+    $_COOKIE['shaarli'] = session_id();
+}
+
 include "inc/rain.tpl.class.php"; //include Rain TPL
 raintpl::$tpl_dir = $GLOBALS['config']['RAINTPL_TPL']; // template directory
 raintpl::$cache_dir = $GLOBALS['config']['RAINTPL_TMP']; // cache directory
diff --git a/tests/UtilsTest.php b/tests/UtilsTest.php
index 5175dde03..0de061b47 100755
--- a/tests/UtilsTest.php
+++ b/tests/UtilsTest.php
@@ -156,7 +156,7 @@ public function testCheckSupportedPHPVersion52()
      */
     public function testIsSessionIdValid()
     {
-        $this->assertTrue(is_session_id_valid('azertyuiop123456789AZERTYUIOP1aA'));
+        $this->assertTrue(is_session_id_valid('iXJWB-H1w439c02a4ff8770d3a652d344-QhXGZlJsBPQnaeAGaG,SmZFcYxYsxtjXdlslXQn8UyHB0ZkGZeiN5ZAsUsR38YcICkTe1197k7pt5g7b10nq2sqp4bfssf'));
     }
 
     /**
@@ -167,5 +167,6 @@ public function testIsSessionIdInvalid()
         $this->assertFalse(is_session_id_valid(''));
         $this->assertFalse(is_session_id_valid(array()));
         $this->assertFalse(is_session_id_valid('c0ZqcWF3VFE2NmJBdm1HMVQ0ZHJ3UmZPbTFsNGhkNHI='));
+        $this->assertFalse(is_session_id_valid('c0asFsAfSffsAOfsdvZqcWF3VFE2d43asfNmJBdm1HMV3a8AsQ0ZHJ3UmZPbTFsNGhkNHI='));
     }
 }