debhelper and dh_installcron: why make them executables?

[Stephane Bortzmeyer <bortzmeyer@pasteur.fr>]

For the first time, I have a cron file for a package. The file is in the 
debian directory:

ezili:~/Debian/packages/bigbrother/bigbrother-1.08a> ls -alt debian/cron.daily 
-rw-r--r--   1 bortz    bortz          75 Dec  8 14:20 debian/cron.daily

And the debian/rules contain:

	dh_installcron

which was put there by dh_make.

But the file installed in debian/tmp is executable:

ezili:~/Debian/packages/bigbrother/bigbrother-1.08a> ls -alt 
debian/tmp/etc/cron.daily/
total 3
drwxr-xr-x   2 bortz    bortz        1024 Dec  8 15:55 .
-rwxr-xr-x   1 bortz    bortz          75 Dec  8 15:55 bigbrother
drwxr-xr-x   4 bortz    bortz        1024 Dec  8 15:55 ..

lintian complains and of course cron does, too:
			
/etc/cron.daily/bigbrother:
run-parts: failed to exec /etc/cron.daily/bigbrother: Exec format error
run-parts: /etc/cron.daily/bigbrother exited with return code 1

Whose fault is it? dh_installcron? (It just calls install without the -m 
option.) Mine?