Install error on ECL

[NOEU]

When I tried to install GSLL using Quicklisp with ECL (Embeddable Common 
Lisp) 16.1.3, the following error occurred and installation failed. I 
use Debian GNU / Linux (buster). Is there a way to solve this problem?
(I'm not native English, I'm sorry if there is a mistake type)


 > (ql:quickload "gsll")
To load "gsll":
   Load 1 ASDF system:
     gsll
; Loading "gsll"
;;; Internal error:
;;;   ** Reader error in file #<input stream 
#P"/home/hiro/deepspace/share/deepspace/quicklisp/dists/quicklisp/software/gsll-quicklisp-eeeda841-git/polynomial.lisp">, 
position 2690:
;;; No dispatch function defined for character #\+
Condition of type: COMPILE-FILE-ERROR
COMPILE-FILE-ERROR while compiling #<cl-source-file "gsll" "polynomial">