Ssh -X through another ssh tunnel

Here's my setup: I have an ssh tunnel running from my local machine through 2 (my external facing box on the LAN) to 3 (internal only on the LAN).



I'm sshing in through the ssh tunnel with the -X option, and I want to start an X program on my internal machine (#3, 192.168.1.103). However, when I execute the program from the shell on #3, it's using the instance of the program that is installed on #1, my local machine. How can I get it to run the program from the remote machine through an ssh session that is going through an ssh tunnel?