Spurious compilation diagnostic?

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CMU Common Lisp 19e (19E), running on gail
With core: /Users/sje/cmucl-19e-x86-darwin/lib/cmucl/lib/lisp.core
Dumped on: Thu, 2008-05-01 20:38:02-04:00 on macmini
See <http://www.cons.org/cmucl/> for support information.
Loaded subsystems:
     Python 1.1, target Intel x86
     CLOS based on Gerd's PCL 2004/04/14 03:32:47


User source (wrapper for read-char):

(defun read-ch (my-stream)
   "Return the next character on an input stream; return nil on end of  
stream."
   (read-char my-stream nil nil))


Compilation warning output:

; In: DEFUN READ-CH

;   (READ-CHAR MY-STREAM NIL NIL)
; --> BLOCK LET LISP::STREAM-DISPATCH ETYPECASE LET COND IF COND IF  
COND IF
; --> PROGN LET
; ==>
;   (STREAM-READ-CHAR STREAM)
; Warning: Undefined function STREAM-READ-CHAR



Is the above a spurious compilation diagnostic?  The user function  
works fine.