Mine was the same too !
Hey,
My passport expires in Jan of 2004 and I went for getting I-551 stamped in september of 2003.
It only dawned iupon me while sitting in the BCIS office that my passport will expire in Jan, so I asked the IIO. She told me it is perfectly OK to have I-551 stamped on an expired passport as long as u got a valid passport, but should I feel that I should also get the new passport tsamped I can go to BCIS office and get it stamped NO PROBLEM.
My suggestion to you is if you know your passport will expire in Jan what the heck are you waiting for, get it renewed man why you waitin' baby ?