diff --git a/hooks/debian/20-setup-apt b/hooks/debian/20-setup-apt
index e008d39..0d9353f 100755
--- a/hooks/debian/20-setup-apt
+++ b/hooks/debian/20-setup-apt
@@ -78,7 +78,7 @@ E_O_APT
 #
 #  If the host system has security support then enable that here too.
 #
-if ( test '!' -e /etc/apt/sources.list || \
+if ( test -e /etc/apt/sources.list && \
      grep ^deb.*security -r /etc/apt/sources.list /etc/apt/sources.list.d >/dev/null 2>/dev/null ) ; then
 
     cat <<E_O_APT >> ${prefix}/etc/apt/sources.list