23.0.60; error "Invalid face slant" roman

[Dan Kruchinin]

Hello.

After I customize default font using set-default-font and customize 
default face using custom-set-faces I get an error:
internal-set-lisp-face-attribute(default :slant roman #<frame 
address@hidden 0xf46800>).
This problem can be reproduced in the following way:
----
(when window-system
 (set-default-font "DejaVu Sans Mono-8"))

(custom-set-faces
  '(default ((t (:foreground "lightgray" :background "black")))))
----

This occurs only if custom-set-faces was used with 'default face. 
Customization of all other faces doesn't produce such error.
Also if I replace (custom-set-faces '(default ((t (:foreground 
"lightgray" :background "black"))))) with both
set-face-foreground and set-face-background to get colors I want, emacs 
doesn't produce this error as well.

Debugger output:
---
Debugger entered--Lisp error: (error "Invalid face slant" roman)
 internal-set-lisp-face-attribute(default :slant roman #<frame 
address@hidden 0xf46800>)
 set-face-attribute(default #<frame address@hidden 0xf46800> :slant roman)
 face-spec-set-2(default #<frame address@hidden 0xf46800> ((t :stipple 
nil :background "white" :foreground "black" :inverse-video nil :box nil 
:strike-through nil :overline nil :underline nil :slant roman :weight 
normal :height 77 :width normal :family "unknown-dejavu sans mono")))
 face-spec-recalc(default #<frame address@hidden 0xf46800>)
 face-spec-set(default ((t (:foreground "lightgray" :background 
"black"))) t)
 custom-theme-set-faces(user (default ((t ...))))
 apply(custom-theme-set-faces user (default ((t ...))))
 custom-set-faces((default ((t ...))))
 eval-buffer(#<buffer  *load*> nil "/home/dk/.emacs" nil t)  ; Reading 
at buffer position 288
 load-with-code-conversion("/home/dk/.emacs" "/home/dk/.emacs" t t)
 load("~/.emacs" t t)
---

Other information:
---
In GNU Emacs 23.0.60.2 (x86_64-unknown-linux-gnu, GTK+ Version 2.12.9)
of 2008-04-08 on midgard
Windowing system distributor `The X.Org Foundation', version 11.0.10300000
configured using `configure  '--prefix=/usr' '--sharedstatedir=/var/lib' 
'--libexecdir=/usr/lib' '--localstatedir=/var/lib' 
'--infodir=/usr/share/info' '--mandir=/usr/share/man' '--with-xpm' 
'--with-jpeg' '--with-tiff' '--with-gif' '--with-gpm' 
'--with-x-toolkit=gtk' '--with-xft=yes' '--enable-font-backend''

Important settings:
 value of $LC_ALL: nil
 value of $LC_COLLATE: nil
 value of $LC_CTYPE: nil
 value of $LC_MESSAGES: nil
 value of $LC_MONETARY: nil
 value of $LC_NUMERIC: nil
 value of $LC_TIME: nil
 value of $LANG: en_US.UTF-8
 value of $XMODIFIERS: nil
 locale-coding-system: utf-8-unix
 default-enable-multibyte-characters: t

Major mode: Debugger

Minor modes in effect:
 tooltip-mode: t
 tool-bar-mode: t
 mouse-wheel-mode: t
 menu-bar-mode: t
 file-name-shadow-mode: t
 global-font-lock-mode: t
 font-lock-mode: t
 blink-cursor-mode: t
 global-auto-composition-mode: t
 auto-composition-mode: t
 auto-compression-mode: t
 line-number-mode: t
 transient-mark-mode: t

Recent input:
M-x e m a <tab> b u <tab> <backspace> <backspace> <backspace>
<backspace> <backspace> <backspace> <backspace> <backspace>
r e <tab> p o <tab> r <tab> <return>

Recent messages:
Entering debugger...
---

W.B.R.
Dan Kruchinin