diff --git a/src/calibre/trac/plugins/download.py b/src/calibre/trac/plugins/download.py
index 43ca425114..1a04a6f6aa 100644
--- a/src/calibre/trac/plugins/download.py
+++ b/src/calibre/trac/plugins/download.py
@@ -428,7 +428,7 @@ def main():
     
     print 'Extracting files to %s ...'%destdir
     extract_tarball(f, destdir)
-    pi = os.path.join(destdir, calibre_postinstall)
+    pi = os.path.join(destdir, 'calibre_postinstall')
     subprocess.call('pi', shell=True)
     return 0
 '''