git blame gives an ambiguous short revision

Using linux-next cloned today (July 1), I then checkout out the
revision 60d5c9f5b.  The command

git blame drivers/staging/brcm80211/brcmfmac/wl_iw.c -L3675,3675

then gives:

60d5c9f5 (Julia Lawall 2011-04-01 16:23:42 +0200 3675)  if (!iscan->iscan_ex_params_p) {

Then I try:

git show 60d5c9f5

which gives:

error: short SHA1 60d5c9f5 is ambiguous.
error: short SHA1 60d5c9f5 is ambiguous.
fatal: ambiguous argument '60d5c9f5': unknown revision or path not in the
working tree.
Use '--' to separate paths from revisions

If I give git blame the -l option, every thing is fine.

thanks,
julia