Index: wp-admin/js/wp-fullscreen.dev.js
===================================================================
--- wp-admin/js/wp-fullscreen.dev.js	(revision )
+++ wp-admin/js/wp-fullscreen.dev.js	(working copy)
@@ -727,7 +727,7 @@ PubSub.prototype.publish = function( topic, args ) {
 		newheight = txt.scrollHeight > 300 ? txt.scrollHeight : 300;
 
 		if ( newheight != api.oldheight ) {
-			txt.style.height = newheight + 'px';
+			txt.style.height = (newheight) + 'px';
 			api.oldheight = newheight;
 		}
 	};