math/R build failed, "No man pages found in package 'Matrix'"

I ran into this on my current i386 bulk build,

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Creating a generic function for 'qr.fitted' from package 'base' in package 'Matrix'
Creating a generic function for 'toeplitz' from package 'stats' in package 'Matrix'
** help
No man pages found in package 'Matrix'
Error in .get_package_metadata(dir, FALSE) :
Files 'DESCRIPTION' and 'DESCRIPTION.in' are missing.
ERROR: installing Rd objects failed for package 'Matrix'
* removing '/pobj/R-4.0.4/build-i386/library/Matrix'
gmake[2]: *** [Makefile:53: Matrix.ts] Error 1
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4.0.4 normally builds OK. Anyone have ideas what's up?