diff --git a/debian/postinst b/debian/postinst
index 00c035a9..300fdf46 100644
--- a/debian/postinst
+++ b/debian/postinst
@@ -18,7 +18,7 @@ case "$1" in
 	# FIXME: Remove with 1.1
 	if test -n "$2"; then
 		if dpkg --compare-versions "$2" 'lt' '0.9.4-1'; then
-			if grep -q  -P -e '^\s\+verify-schedule ' /etc/proxmox-backup/datastore.cfg; then
+			if grep -s -q  -P -e '^\s+verify-schedule ' /etc/proxmox-backup/datastore.cfg; then
 				echo "NOTE: drop all verify schedules from datastore config."
 				echo "You can now add more flexible verify jobs"
 				flock -w 30 /etc/proxmox-backup/.datastore.lck \