Spec generation fails on OpenBSD

[rpx99]

I am trying to generate spec files. Unfortunately this fails.

tron$ sbcl --load "sdl2-image.asd" --eval "(ql:quickload '(:sdl2-image))" --eval "(uiop:quit)" 
This is SBCL 2.4.8.openbsd.sbcl-2.4.8, an implementation of ANSI Common Lisp.
More information about SBCL is available at <http://www.sbcl.org/>.

SBCL is free software, provided as is, with absolutely no warranty.
It is mostly in the public domain; some portions are provided under
BSD-style licenses.  See the CREDITS and COPYING files in the
distribution for more information.
To load "sdl2-image":
  Load 1 ASDF system:
    sdl2-image
; Loading "sdl2-image"
..................; 
; caught ERROR:
;   READ error during COMPILE-FILE:
;   
;     Symbol "IMG-INIT-FLAGS" not found in the SDL2-FFI package.
;   
;       Line: 7, Column: 73, File-Position: 259
;   
;       Stream: #<SB-INT:FORM-TRACKING-STREAM for "file /home/rpx/common-lisp/cl-sdl2-image/src/general.lisp" {1101E12EB3}>

debugger invoked on a UIOP/LISP-BUILD:COMPILE-FILE-ERROR in thread
#<THREAD tid=101673 "main thread" RUNNING {1100BE80A3}>:
  COMPILE-FILE-ERROR while compiling #<CL-SOURCE-FILE "sdl2-image" "general">

Help appreciated...