diff --git a/system/libraries/Session/drivers/Session_memcached_driver.php b/system/libraries/Session/drivers/Session_memcached_driver.php
index e924644..ab3b1d9 100644
--- a/system/libraries/Session/drivers/Session_memcached_driver.php
+++ b/system/libraries/Session/drivers/Session_memcached_driver.php
@@ -209,7 +209,6 @@
 			$this->_memcached->replace($this->_lock_key, time(), 300);
 			if ($this->_fingerprint !== ($fingerprint = md5($session_data)))
 			{
-
 				if (
 					$this->_memcached->replace($key, $session_data, $this->_config['expiration'])
 					OR ($this->_memcached->getResultCode() === Memcached::RES_NOTSTORED && $this->_memcached->set($key, $session_data, $this->_config['expiration']))
@@ -222,9 +221,13 @@
 				return $this->_failure;
 			}
 
-			return $this->_memcached->touch($this->_key_prefix.$session_id, $this->_config['expiration'])
-				? $this->_success
-				: $this->_failure;
+			if (
+				$this->_memcached->touch($key, $this->_config['expiration'])
+				OR ($this->_memcached->getResultCode() === Memcached::RES_NOTFOUND && $this->_memcached->set($key, $session_data, $this->_config['expiration']))
+			)
+			{
+				return $this->_success;
+			}
 		}
 
 		return $this->_failure;
diff --git a/user_guide_src/source/changelog.rst b/user_guide_src/source/changelog.rst
index cd18599..e9a265f 100644
--- a/user_guide_src/source/changelog.rst
+++ b/user_guide_src/source/changelog.rst
@@ -29,6 +29,7 @@
 -  Fixed a bug (#4424) - :doc:`Session Library <libraries/sessions>` triggered a PHP warning when writing a newly created session with the 'redis' driver.
 -  Fixed a bug (#4437) - :doc:`Inflector Helper <helpers/inflector_helper>` function :php:func:`humanize()` didn't escape its ``$separator`` parameter while using it in a regular expression.
 -  Fixed a bug where :doc:`Session Library <libraries/sessions>` didn't properly handle its locks' statuses with the 'memcached' driver.
+-  Fixed a bug where :doc:`Session Library <libraries/sessions>` triggered a PHP warning when writing a newly created session with the 'memcached' driver.
 
 Version 3.0.4
 =============