Index: t3lib/config_default.php
===================================================================
--- t3lib/config_default.php	(revision 5253)
+++ t3lib/config_default.php	(working copy)
@@ -67,6 +67,7 @@
 		'devIPmask' => '127.0.0.1,::1',			// Defines a list of IP addresses which will allow development-output to display. The debug() function will use this as a filter. See the function t3lib_div::cmpIP() for details on syntax. Setting this to blank value will deny all. Setting to "*" will allow all.
 		'sqlDebug' => 0,						// Boolean. If set, then database queries that fails are outputted in browser. For development.
 		'enable_DLOG' => FALSE,					// Whether the developer log is enabled. See constant "TYPO3_DLOG"
+		'enableDeprecationLogFile' => TRUE,		// Boolean. Whether the deprecration logfile at typo3conf/deprecation_*.log is enabled.
 		'ddmmyy' => 'd-m-y',					// Format of Date-Month-Year - see PHP-function date()
 		'hhmm' => 'H:i',						// Format of Hours-Minutes - see PHP-function date()
 		'USdateFormat' => 0,					// Boolean. If true, dates entered in the TCEforms of the backend will be formatted mm-dd-yyyy
Index: t3lib/class.t3lib_div.php
===================================================================
--- t3lib/class.t3lib_div.php	(revision 5253)
+++ t3lib/class.t3lib_div.php	(working copy)
@@ -5269,15 +5269,18 @@
 	 * @return	void
 	 */
 	public static function deprecationLog($msg) {
-		// write a longer message to the deprecation log
-		$destination = PATH_typo3conf . '/deprecation_' . t3lib_div::shortMD5(PATH_site . $GLOBALS['TYPO3_CONF_VARS']['SYS']['encryptionKey']) . '.log';
-		$file = @fopen($destination, 'a');
-		if ($file) {
-			$date = date($GLOBALS['TYPO3_CONF_VARS']['SYS']['ddmmyy'] . ' ' . $GLOBALS['TYPO3_CONF_VARS']['SYS']['hhmm'] . ': ');
-			flock($file, LOCK_EX);  // try locking, but ignore if not available (eg. on NFS and FAT)
-			@fwrite($file, $date.$msg.chr(10));
-			flock($file, LOCK_UN);    // release the lock
-			@fclose($file);
+		// Write to deprecation logfile if not disabled
+		if ($GLOBALS['TYPO3_CONF_VARS']['SYS']['enableDeprecationLogFile']) {
+			// write a longer message to the deprecation log
+			$destination = PATH_typo3conf . '/deprecation_' . t3lib_div::shortMD5(PATH_site . $GLOBALS['TYPO3_CONF_VARS']['SYS']['encryptionKey']) . '.log';
+			$file = @fopen($destination, 'a');
+			if ($file) {
+				$date = date($GLOBALS['TYPO3_CONF_VARS']['SYS']['ddmmyy'] . ' ' . $GLOBALS['TYPO3_CONF_VARS']['SYS']['hhmm'] . ': ');
+				flock($file, LOCK_EX);  // try locking, but ignore if not available (eg. on NFS and FAT)
+				@fwrite($file, $date.$msg.chr(10));
+				flock($file, LOCK_UN);    // release the lock
+				@fclose($file);
+			}
 		}
 
 		// copy message also to the developer log