How to replace a single corrupt, packed object?

Hi,

my auto gc kicked in, and shows this:

fatal: corrupt packed object for 2c1e128aa51e3a64bd61556c0cd488628b423ccf
error: failed to run repack

Fortunately, I have the uncorrupted object somewhere else.  So I copy the 
single object as a loose one, and all is fine.  Right?

Wrong.

Repack still picks up the corrupt object instead of the good one.  What's 
the best way out?

Ciao,
Dscho