drush make issues with unzipping fullcalendar library

First an example make file called 'fullcalendar.make'

core = 7.16
api = 2

libraries[fullcalendar][download][type] = get
libraries[fullcalendar][download][url] = http://arshaw.com/fullcalendar/downloads/fullcalendar-1.5.3.zip
libraries[fullcalendar][download][sha1] = c7219b1ddd2b11ccdbf83ebd116872affbc45d7a
libraries[fullcalendar][download][subtree] = fullcalendar

Then we execute that and below is what we get;

jeff@ubuntu:~$ drush --verbose make --no-core fullcalendar.make testdir
Loading release_info engine.                                                                                                  [notice]
Executing: which wget
Executing: wget -q --timeout=30 -O /tmp/download_fileUHS4o2 http://arshaw.com/fullcalendar/downloads/fullcalendar-1.5.3.zip
fullcalendar downloaded from http://arshaw.com/fullcalendar/downloads/fullcalendar-1.5.3.zip.                                 [ok]
Mime type for /tmp/make_tmp_1350672338_50819fd21ca7f/fullcalendar-1.5.3.zip is application/zip                                [notice]
Mime type for /tmp/make_tmp_1350672338_50819fd21ca7f/fullcalendar-1.5.3.zip is application/zip                                [notice]
Executing: unzip /tmp/make_tmp_1350672338_50819fd21ca7f/fullcalendar-1.5.3.zip -d /tmp/drush_tmp_1350672339_50819fd31d083
Directory fullcalendar not found within /tmp/make_tmp_1350672338_50819fd21ca7f/fullcalendar-1.5.3.                            [error]
Command dispatch complete                                                                                                     [notice]

Now attempting to check what drush did;

jeff@ubuntu:~$ cd /tmp/
jeff@ubuntu:/tmp$ wget -q -O /tmp/fc.zip http://arshaw.com/fullcalendar/downloads/fullcalendar-1.5.3.zip
jeff@ubuntu:/tmp$ unzip fc.zip 
Archive:  fc.zip
   creating: fullcalendar-1.5.3/
  inflating: fullcalendar-1.5.3/changelog.txt  
   creating: fullcalendar-1.5.3/demos/
  inflating: fullcalendar-1.5.3/demos/agenda-views.html  
  inflating: fullcalendar-1.5.3/demos/basic-views.html  
   creating: fullcalendar-1.5.3/demos/cupertino/
   creating: fullcalendar-1.5.3/demos/cupertino/images/
 extracting: fullcalendar-1.5.3/demos/cupertino/images/ui-bg_diagonals-thick_90_eeeeee_40x40.png  
  inflating: fullcalendar-1.5.3/demos/cupertino/images/ui-bg_flat_15_cd0a0a_40x100.png  
  inflating: fullcalendar-1.5.3/demos/cupertino/images/ui-bg_glass_100_e4f1fb_1x400.png  
 extracting: fullcalendar-1.5.3/demos/cupertino/images/ui-bg_glass_50_3baae3_1x400.png  
  inflating: fullcalendar-1.5.3/demos/cupertino/images/ui-bg_glass_80_d7ebf9_1x400.png  
 extracting: fullcalendar-1.5.3/demos/cupertino/images/ui-bg_highlight-hard_100_f2f5f7_1x100.png  
  inflating: fullcalendar-1.5.3/demos/cupertino/images/ui-bg_highlight-hard_70_000000_1x100.png  
  inflating: fullcalendar-1.5.3/demos/cupertino/images/ui-bg_highlight-soft_100_deedf7_1x100.png  
  inflating: fullcalendar-1.5.3/demos/cupertino/images/ui-bg_highlight-soft_25_ffef8f_1x100.png  
  inflating: fullcalendar-1.5.3/demos/cupertino/images/ui-icons_2694e8_256x240.png  
  inflating: fullcalendar-1.5.3/demos/cupertino/images/ui-icons_2e83ff_256x240.png  
  inflating: fullcalendar-1.5.3/demos/cupertino/images/ui-icons_3d80b3_256x240.png  
  inflating: fullcalendar-1.5.3/demos/cupertino/images/ui-icons_72a7cf_256x240.png  
  inflating: fullcalendar-1.5.3/demos/cupertino/images/ui-icons_ffffff_256x240.png  
  inflating: fullcalendar-1.5.3/demos/cupertino/theme.css  
  inflating: fullcalendar-1.5.3/demos/default.html  
  inflating: fullcalendar-1.5.3/demos/external-dragging.html  
  inflating: fullcalendar-1.5.3/demos/gcal.html  
  inflating: fullcalendar-1.5.3/demos/json-events.php  
  inflating: fullcalendar-1.5.3/demos/json.html  
  inflating: fullcalendar-1.5.3/demos/selectable.html  
  inflating: fullcalendar-1.5.3/demos/theme.html  
   creating: fullcalendar-1.5.3/fullcalendar/
  inflating: fullcalendar-1.5.3/fullcalendar/fullcalendar.css  
  inflating: fullcalendar-1.5.3/fullcalendar/fullcalendar.js  
  inflating: fullcalendar-1.5.3/fullcalendar/fullcalendar.min.js  
  inflating: fullcalendar-1.5.3/fullcalendar/fullcalendar.print.css  
  inflating: fullcalendar-1.5.3/fullcalendar/gcal.js  
  inflating: fullcalendar-1.5.3/GPL-LICENSE.txt  
   creating: fullcalendar-1.5.3/jquery/
  inflating: fullcalendar-1.5.3/jquery/jquery-1.7.1.min.js  
  inflating: fullcalendar-1.5.3/jquery/jquery-ui-1.8.17.custom.min.js  
  inflating: fullcalendar-1.5.3/MIT-LICENSE.txt  
jeff@ubuntu:/tmp$ ls fullcalendar-1.5.3/
changelog.txt  demos  fullcalendar  GPL-LICENSE.txt  jquery  MIT-LICENSE.txt
jeff@ubuntu:/tmp$ 

I'm a bit confused as to what is going on here. The odd thing is that this works fine for the following make file 'nivoslider.make';

core = 7.16
api = 2

libraries[nivo-slider][download][type] = get
libraries[nivo-slider][download][url] = https://github.com/downloads/gilbitron/Nivo-Slider/nivo-slider2.7.1.zip
libraries[nivo-slider][download][sha1] = bd8e14b82f5b9c6f533a4e1aa26a790cd66c3cb9
libraries[nivo-slider][download][subtree] = nivo-slider

drush output

jeff@ubuntu:/tmp$ drush make --no-core nivoslider.make ns
nivo-slider downloaded from https://github.com/downloads/gilbitron/Nivo-Slider/nivo-slider2.7.1.zip.    [ok]
jeff@ubuntu:/tmp$ ls ns/sites/all/libraries/nivo-slider/
demo  jquery.nivo.slider.js  jquery.nivo.slider.pack.js  license.txt  nivo-slider.css  README  themes
jeff@ubuntu:/tmp$ 

Any help is appreciated, and FWIW we are using both fullcalendar and nivo-slider libraries in julio.