Line 386 of /etc/rc.d/init.d/isdn from isdn-config-0.17-7 reads if [ -n "SLAVE_TRIGGER" ]; then which tests if a fixed string is of non-zero length. This should probably be if [ -n "$SLAVE_TRIGGER" ]; then so that variable expansion takes place on $SLAVE_TRIGGER. Note that $SLAVE_TRIGGER is used in the following line in the script in the following fashion: log_isdnctrl trigger $slave $SLAVE_TRIGGER
It's fixed. you will find it in rawhide soon. thanks