Use the old #'labels implementation if #'lexical-let changes lambdas. lisp/ChangeLog addition: 2011-12-13 Aidan Kehoe <kehoea@parhasard.net> * bytecomp.el (byte-compile-initial-macro-environment): If lexical let has played with our lambas, give up on constructing the compiled functions at compiled time, that strategy doesn't work.