diff --git a/typo3/sysext/cms/tslib/class.tslib_feuserauth.php b/typo3/sysext/cms/tslib/class.tslib_feuserauth.php
index f20544d..6cc6184 100644
--- a/typo3/sysext/cms/tslib/class.tslib_feuserauth.php
+++ b/typo3/sysext/cms/tslib/class.tslib_feuserauth.php
@@ -399,13 +399,15 @@ class tslib_feUserAuth extends t3lib_userAuth {
 		}
 		if ($this->sesData_change)	{
 			if ($this->id)	{
-				$insertFields = array (
-					'hash' => $this->id,
-					'content' => serialize($this->sesData),
-					'tstamp' => $GLOBALS['EXEC_TIME'],
-				);
 				$this->removeSessionData();
-				$GLOBALS['TYPO3_DB']->exec_INSERTquery('fe_session_data', $insertFields);
+				if (!empty($this->sesData)) {
+					$insertFields = array (
+						'hash' => $this->id,
+						'content' => serialize($this->sesData),
+						'tstamp' => $GLOBALS['EXEC_TIME'],
+					);
+					$GLOBALS['TYPO3_DB']->exec_INSERTquery('fe_session_data', $insertFields);
+				}
 			}
 		}
 	}
@@ -463,23 +465,31 @@ class tslib_feUserAuth extends t3lib_userAuth {
 	 * Notice: Simply calling this function will not save the data to the database! The actual saving is done in storeSessionData() which is called as some of the last things in index_ts.php. So if you exit before this point, nothing gets saved of course! And the solution is to call $GLOBALS['TSFE']->storeSessionData(); before you exit.
 	 *
 	 * @param	string		Session data type; Either "user" (persistent, bound to fe_users profile) or "ses" (temporary, bound to current session cookie)
-	 * @param	string		Key from the data array to store incoming data in; The session data (in either case) is an array ($this->uc / $this->sesData) and this value determines in which key the $data value will be stored.
+	 * @param	string		Key from the data array to store incoming data in; The session data (in either case) is an array ($this->uc / $this->sesData) and this value determines in which key the $data value will be stored. If data is NULL, the key is removed
 	 * @param	mixed		The data value to store in $key
 	 * @return	void
 	 * @see setKey(), storeSessionData(), record_registration()
 	 */
-	function setKey($type,$key,$data)	{
-		if ($key)	{
-			switch($type)	{
+	function setKey($type, $key, $data) {
+		if ($key) {
+			switch($type) {
 				case 'user':
 					if ($this->user['uid'])	{
-						$this->uc[$key]=$data;
-						$this->userData_change=1;
+						if ($data === NULL) {
+							unset($this->uc[$key]);
+						} else {
+							$this->uc[$key] = $data;
+						}
+						$this->userData_change = 1;
 					}
 				break;
 				case 'ses':
-					$this->sesData[$key]=$data;
-					$this->sesData_change=1;
+					if ($data === NULL) {
+						unset($this->sesData[$key]);
+					} else {
+						$this->sesData[$key] = $data;
+					}
+					$this->sesData_change = 1;
 				break;
 			}
 		}