not all tests pass when on an NFS partition

When I run 'make test' for git-1.6.1.3 it will fail on this test when
running on an NFS partition.
Is this a known problem? Is this a real problem?

My uname -a: Linux XXX 2.6.18-92.1.17.el5 #1 SMP Tue Nov 4 13:45:01
EST 2008 i686 athlon i386 GNU/Linux


*** t5304-prune.sh ***
*   ok 1: setup
*   ok 2: prune stale packs
*   ok 3: prune --expire
* FAIL 4: gc: implicit prune --expire


                before=$(git count-objects | sed "s/ .*//") &&
                BLOB=$(echo aleph_0 | git hash-object -w --stdin) &&
                BLOB_FILE=.git/objects/$(echo $BLOB | sed "s/^../&\//") &&
                test $((1 + $before)) = $(git count-objects | sed "s/ .*//") &&
                test -f $BLOB_FILE &&
                test-chmtime =-$((86400*14-30)) $BLOB_FILE &&
                git gc &&
                test $((1 + $before)) = $(git count-objects | sed "s/ .*//") &&
                test -f $BLOB_FILE &&
                test-chmtime =-$((86400*14+1)) $BLOB_FILE &&
                git gc &&
                test $before = $(git count-objects | sed "s/ .*//") &&
                ! test -f $BLOB_FILE