Unable to redefine imported symbols in r7rs library

I found this while playing with some code from chibi. The simplified code is like this

‌

(define-library (abc)
  (import (scheme base) (srfi 1))
  (export everyx)
  (begin
    (define (every) #f)
    (define everyx every)))

and it fails to build

‌

$ ./build/sagittarius -r7 -L . -e '(import (abc))'
Unhandled exception
  Condition components:
  1. &compile
    program: (import (abc))
    source: #f
  2. &compile
    program: (define-library (abc) (import (scheme base) (srfi 1)) (expor
    source: "/home/pclouds/W/sagittarius-scheme/abc.scm":1
  3. &syntax
    subform: (every)
    form: (define (every) #f)
  4. &message attempt to modify immutable variable
  5. &stack-trace

because “every” is already defined in (srfi 1) and I attempt to redefine it.

I have not read r7rs-small again, but I don’t think redefining symbols is forbidden. At least it used to work like that in r5rs. It’s not a competition, but as far I can test, Gauche, Chibi and Larceny all accept this code.

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