Modified   lisp/comint.el
diff --git a/lisp/comint.el b/lisp/comint.el
index cff9afe..a9e9fbd 100644
--- a/lisp/comint.el
+++ b/lisp/comint.el
@@ -3146,6 +3146,8 @@ See `completion-table-with-quoting' and `comint-unquote-function'.")
            #'comint-completion-file-name-table
            comint-unquote-function
            comint-requote-function)))
+    (if (numberp filesuffix)
+        (setq filesuffix (char-to-string filesuffix)))
     (nconc
      (list
       filename-beg filename-end