diff --git a/debian/knockd.service b/debian/knockd.service
index 48d51bd..11795f6 100644
--- a/debian/knockd.service
+++ b/debian/knockd.service
@@ -10,7 +10,7 @@ ExecStart=/usr/sbin/knockd $KNOCKD_OPTS
 ExecReload=/bin/kill -HUP $MAINPID
 KillMode=mixed
 SuccessExitStatus=0 2 15
-ProtectSystem=full
+ProtectSystem=true
 CapabilityBoundingSet=CAP_NET_RAW CAP_NET_ADMIN CAP_SYS_MODULE
 
 [Install]