Index: Classes/Service/Fehooks.php
===================================================================
--- Classes/Service/Fehooks.php	(revision 4180)
+++ Classes/Service/Fehooks.php	(working copy)
@@ -41,7 +41,7 @@
 			return;
 		}
 
-		echo $GLOBALS['TSFE']->cObj->cObjGetSingle(
+		$GLOBALS['TSFE']->content .= $GLOBALS['TSFE']->cObj->cObjGetSingle(
 			'FLUIDTEMPLATE',
 			array(
 				'file' => 'EXT:workspaces/Resources/Private/Templates/Preview/Preview.html',