Evaluate "(sdl:with-init () (sdl:with-font (new-font sdl:*font-9x15*) nil))"

I would expect with-init to quietly return nil, but instead I get the following 
condition:

"There is no applicable method for the generic function
  #<STANDARD-GENERIC-FUNCTION LISPBUILDER-SDL:FREE (3)>
when called with arguments
  (#<LISPBUILDER-SDL:SDL-BITMAP-FONT {10079BB093}>).
   [Condition of type SIMPLE-ERROR]"

I am using lispbuilder-sdl 1.2.14 with sbcl 1.1.6.