Install error on ECL

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">