Problem with type conflict style warning

Hello

I don't understand this style warning...

Here is the code (problem with test1 only) :
"
(ql:quickload :alexandria)
(use-package :alexandria)

(defvar *l* '(1 2 3))

(defun test1 ()
  (copy-sequence 'vector (reverse *l*)))

(defun test2 ()
  (copy-sequence 'vector *l*))

(defun test3 ()
  (copy-sequence 'vector '(1 2 3)))

(defun test4 ()
  (let ((l '(1 2 3)))
    (copy-sequence 'vector l)))
"

And here is the result :
"
; in: DEFUN TEST1
;     (COPY-SEQUENCE 'VECTOR (REVERSE *L*))
; --> BLOCK IF COERCE 
; ==>
;   1
; 
; caught STYLE-WARNING:
;   Derived type of SB-C::X is
;     (VALUES (OR LIST SB-KERNEL:EXTENDED-SEQUENCE) &OPTIONAL),
;   conflicting with its asserted type
;     VECTOR.
;   See also:
;     The SBCL Manual, Node "Handling of Types"
"

sbcl 2.4.1 and 2.4.4 (other versions not tested).

I have the same problem with remove-if-not instead of reverse.

Thank you

syll