U.S. Citizenship and Immigration Services (USCIS) has published an update to Form I-751, Petition to Remove Conditions on Residence. The new edition is dated 11/23/15.
Beginning on February 29, 2016, USCIS will accept only the 11/23/15 edition. The edition date is at the bottom of every page of the form and instructions. The expiration date at the top says 11/30/2017.