lexical scoping rule

[GRAME@AppleLink.Apple.COM (France - Grame, Lyon,IDV)]

The lexical scoping rule seems to have strange behaviours in MCL2.0 (or may be
it's Common Lisp).
 
The first example is ok :
 
 ? (defun compose (x y) #'(lambda (n) (funcall x (funcall y n))))
 COMPOSE
 
 ? (funcall (compose #'sqrt #'abs) -9)
 3
 
But now :
 
 ? (defvar x 13)
 X
 
 ? (defun compose (x y) #'(lambda (n) (funcall x (funcall y n))))
 COMPOSE
 
 ? (funcall (compose #'sqrt #'abs) -9)
 > Error: 13 can't be FUNCALLed or APPLYed.
 > While executing: CCL::TOPLEVEL-EVAL
 > Type Command-. to abort.
 See the Restarts... menu item for further choices.
 
Because of the DEFVAR, the X variable is no more part of the closure of the
lambda-expression.
 
It seems to me to be a bug because the X variable visible to the
lambda-expression is lexically scoped.
 
-Yann-