cannot rebind Control-u

[pm]

Configuration Information [Automatically generated, do not change]:
Machine: i586
OS: linux
Compiler: gcc -I/usr/src/packages/BUILD/bash-3.1 
-L/usr/src/packages/BUILD/bash-3.1/../readline-5.1
Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='i586' 
-DCONF_OSTYPE='linux' -DCONF_MACHTYPE='i586-suse-linux' -DCONF_VENDOR='suse' 
-DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash' -DSHELL -DHAVE_CONFIG_H   -I.  
-I. -I./include -I./lib   -O2 -march=i586 -mtune=i686 -fmessage-length=0 -Wall 
-D_FORTIFY_SOURCE=2 -g -D_GNU_SOURCE -DRECYCLES_PIDS -Wall -pipe -g 
-fbranch-probabilities
uname output: Linux gaston 2.6.16.13-4 #1 SMP Thu Jun 22 17:44:56 CEST 2006 
i686 i686 i386 GNU/Linux
Machine Type: i586-suse-linux

Bash Version: 3.1
Patch Level: 17
Release Status: release

Description:
        In my $HOME/.inputrc I have the line
        Control-u: undo
        This used to work well with earlier versions of bash, but now,
        the C-u key cannot be removed from the function unix-line-discard.

Repeat-By:
        bind Control-i:undo
        bind -P | grep undo