Index: t3lib/error/class.t3lib_error_debugexceptionhandler.php
===================================================================
--- t3lib/error/class.t3lib_error_debugexceptionhandler.php	(Revision 10521)
+++ t3lib/error/class.t3lib_error_debugexceptionhandler.php	(Arbeitskopie)
@@ -54,7 +54,11 @@
 	 */
 	public function echoExceptionWeb(Exception $exception) {
 		if (!headers_sent()) {
-			header("HTTP/1.1 500 Internal Server Error");
+				// make sure that we do not overwrite a previously created status header
+			$headerList = headers_list();
+			if (count($headerList) == 0 || substr($headerList[0], 0, 7) === 'HTTP/1.') {
+				header("HTTP/1.1 500 Internal Server Error");
+			}
 		}
 
 		$filePathAndName = $exception->getFile();
Index: t3lib/error/class.t3lib_error_productionexceptionhandler.php
===================================================================
--- t3lib/error/class.t3lib_error_productionexceptionhandler.php	(Revision 10521)
+++ t3lib/error/class.t3lib_error_productionexceptionhandler.php	(Arbeitskopie)
@@ -51,7 +51,11 @@
 	 */
 	public function echoExceptionWeb(Exception $exception) {
 		if (!headers_sent()) {
-			header("HTTP/1.1 500 Internal Server Error");
+				// make sure that we do not overwrite a previously created status header
+			$headerList = headers_list();
+			if (count($headerList) == 0 || substr($headerList[0], 0, 7) === 'HTTP/1.') {
+				header("HTTP/1.1 500 Internal Server Error");
+			}
 		}
 		$this->writeLogEntries($exception, self::CONTEXT_WEB);
 			// we use a nice-looking title for our visitors instead of the exception's class name