xconfig fails when compiling 2.56 or 2.57-pre1

I find that during a compile of either 2.5.6 or 2.5.7-pre1 I get the
following error:

Compiling kernel-2.5.7-pre1

make clean...
OK

make distclean...
OK

make mrproper...
OK

make xconfig...
sound/core/Config.in: 4: can't handle dep_bool/dep_mbool/dep_tristate condition make[1]: *** [kconfig.tk] Error 1
make: *** [xconfig] Error 2
NOT OK

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