./sbcl --core ../lib/sbcl/sbcl.core --load ~/hejmo/elŝ/dat/quicklisp.lisp
This is SBCL 1.3.13.nixos, an implementation of ANSI Common Lisp.
More information about SBCL is available at <http://www.sbcl.org/>.

SBCL is free software, provided as is, with absolutely no warranty.
It is mostly in the public domain; some portions are provided under
BSD-style licenses.  See the CREDITS and COPYING files in the
distribution for more information.
While evaluating the form starting at line 314, column 0
  of #P"/home/mel/hejmo/elŝ/dat/quicklisp.lisp":

debugger invoked on a SB-FASL::INVALID-FASL-VERSION in thread
#<THREAD "main thread" RUNNING {1001BBEC13}>:
  #<SB-SYS:FD-STREAM for "file /nix/store/i2m51k7xypfmscgsrv6szah22vxqyl1b-sbcl-1.2.5/lib/sbcl/contrib/sb-bsd-sockets.fasl" {10026EEEF3}>
  is a fasl file compiled with SBCL 1.2.5.nixos, and can't be loaded into SBCL
  1.3.13.nixos.

Type HELP for debugger help, or (SB-EXT:EXIT) to exit from SBCL.

restarts (invokable by number or by possibly-abbreviated name):
  0: [CONTINUE] Load the fasl file anyway
  1: [RETRY   ] Retry EVAL of current toplevel form.
  2:            Ignore error and continue loading file "/home/mel/hejmo/elŝ/dat/quicklisp.lisp".
  3: [ABORT   ] Abort loading file "/home/mel/hejmo/elŝ/dat/quicklisp.lisp".
  4:            Ignore runtime option --load "/home/mel/hejmo/elŝ/dat/quicklisp.lisp".
  5:            Skip rest of --eval and --load options.
  6:            Skip to toplevel READ/EVAL/PRINT loop.
  7: [EXIT    ] Exit SBCL (calling #'EXIT, killing the process).

(SB-FASL::CHECK-FASL-HEADER #<SB-SYS:FD-STREAM for "file /nix/store/i2m51k7xypfmscgsrv6szah22vxqyl1b-sbcl-1.2.5/lib/sbcl/contrib/sb-bsd-sockets.fasl" {10026EEEF3}>)