I am trying mcclim and cffi from Debian unstable in SBCL. I cannot load gtkairo

CL-USER(1): (require :mcclim)

; loading system definition from /usr/share/common-lisp/systems/flexichain.asd
; into #<PACKAGE "ASDF0">
; registering #<SYSTEM :FLEXICHAIN {1004742611}> as FLEXICHAIN
; loading system definition from
; /usr/share/common-lisp/systems/spatial-trees.asd into #<PACKAGE "ASDF0">
; registering #<SYSTEM :SPATIAL-TREES {1004A49081}> as SPATIAL-TREES
; loading system definition from /usr/share/common-lisp/systems/clx.asd into
; #<PACKAGE "ASDF0">
; registering #<SYSTEM CLX {1004BCF731}> as CLX
NIL
CL-USER(2): (require :clim-gtkairo)

; compiling file "/usr/share/common-lisp/source/mcclim/Backends/gtkairo/gtk-ffi.lisp" (written 03 MAR 2007 07:09:51 AM):
; compiling (IN-PACKAGE :CLIM-GTKAIRO)
; compiling (CFFI:DEFCTYPE UTF8-STRING ...)
debugger invoked on a SIMPLE-ERROR in thread #<THREAD "initial thread" {1004273D61}>:
Unknown CFFI type: (:STRING :ENCODING :UTF-8).

Type HELP for debugger help, or (SB-EXT:QUIT) to exit from SBCL.

restarts (invokable by number or by possibly-abbreviated name):
0: [RETRY ] Retry performing #<ASDF:COMPILE-OP NIL {1005A90811}> on
              #<ASDF:CL-SOURCE-FILE "gtk-ffi" {10086C5801}>.
1: [ACCEPT] Continue, treating #<ASDF:COMPILE-OP NIL {1005A90811}> on
              #<ASDF:CL-SOURCE-FILE "gtk-ffi" {10086C5801}> as having been
              successful.
2: [ABORT ] Exit debugger, returning to top level.

(CFFI::PARSE-TYPE (:STRING :ENCODING :UTF-8))
0]

ii cl-cffi                    20061013-1                 The Common Foreign Function Interface for Common Lisp
ii cl-mcclim                  0.9.5.dfsg.1-1              Common Lisp graphic user interface toolkit

Is the CFFI too old here?

Liam