We prove the undecidability of Core XPath 1.0 (CXP) [G. Gottlob and C. Koch,inProc. of 17th Ann. IEEE Symp. on Logic in Computer Science,LICS ’02(Copenhagen,July 2002). IEEE CS Press (2002) 189–202.] extended with anInflationary Fixed Point (IFP) operator. More specifically,we provethat the satisfiability problem of this language is undecidable. In fact,the fragment ofCXP+IFP containing only the self and descendant axes is already undecidable.