Compiler macro docstring overwrites docstring of function.

The docstring of compiler macro seems to overwrite that of the corresponding function.

(defun foo (x)
  "function docstring"
  nil)

(define-compiler-macro foo ()
  "compiler-macro docstring"
  nil)

(documentation 'foo 'compiler-macro)
; => NIL
(documentation 'foo 'function)
; => "compiler-macro docstring"

Expected results:

(documentation 'foo 'compiler-macro)
; => "compiler-macro docstring"
(documentation 'foo 'function)
; => "function docstring"

Provide details regarding ECL version (or preferably commit), operating system and if revelant the build options and versions of the build tools.

     VERSION "20.4.24"
      VCS-ID "UNKNOWN"
          OS "Linux"
  OS-VERSION "5.10.46-4rodete4-amd64"
MACHINE-TYPE "x86_64"
    FEATURES (:SWANK :SERVE-EVENT :QUICKLISP :ASDF-PACKAGE-SYSTEM :ASDF3.1
              :ASDF3 :ASDF2 :ASDF :OS-UNIX :NON-BASE-CHARS-EXIST-P
              :ASDF-UNICODE :WALKER :CDR-1 :CDR-5 :LINUX :FORMATTER :CDR-7
              :ECL-WEAK-HASH :LITTLE-ENDIAN :ECL-READ-WRITE-LOCK :LONG-LONG
              :UINT64-T :UINT32-T :UINT16-T :COMPLEX-FLOAT :LONG-FLOAT :UNICODE
              :DFFI :CLOS-STREAMS :CMU-FORMAT :UNIX :ECL-PDE :DLOPEN :CLOS
              :THREADS :BOEHM-GC :ANSI-CL :COMMON-LISP
              :FLOATING-POINT-EXCEPTIONS :IEEE-FLOATING-POINT
              :PACKAGE-LOCAL-NICKNAMES :CDR-14 :PREFIXED-API :FFI :X86_64
              :COMMON :ECL)