git gc exit with out of memory, malloc failed error

I'm new to git and I'm getting the following out of memory error on git gc:

$ git gc Counting objects: 80818, done. Delta compression using up to 8 threads. fatal: Out of memory, malloc failed (tried to allocate 24359675 bytes) error: failed to run repack

The only advice I found in the internet suggested to run repack with --window-memory parameter specified. But this call also fails:

$ git repack -adf --window-memory=0 Counting objects: 80818, done. Delta compression using up to 8 threads. warning: suboptimal pack - out of memory fatal: Out of memory, malloc failed (tried to allocate 24356363 bytes)

How do I cleanup my repository?

$ git version git version 1.7.6.msysgit.0

OS: Windows Server 2008 R2 SP1 (x64)
Physical memory: 24 GB
The commands listed were executed under x64 console process.