diff --git a/dhcp-to-dns b/dhcp-to-dns
index dfb438f..83e312f 100644
--- a/dhcp-to-dns
+++ b/dhcp-to-dns
@@ -25,12 +25,13 @@
    [ $IfThenElse ($HostNameInZone = true) ($Identity . ".") ] . $Domain);
 :local Ttl 5m;
 :local CommentPrefix "managed by dhcp-to-dns for ";
+:local CommentString "--- dhcp-to-dns above ---";
 
-:if ([ :len [ / ip dns static find where comment="--- dhcp-to-dns above ---" name=- type=NXDOMAIN disabled ] ] = 0) do={
-  / ip dns static add comment="--- dhcp-to-dns above ---" name=- type=NXDOMAIN disabled=yes;
-  $LogPrintExit2 warning $0 ("Added disabled static dns record with comment '--- dhcp-to-dns above ---'.") false;
+:if ([ :len [ / ip dns static find where comment=$CommentString name=- type=NXDOMAIN disabled ] ] = 0) do={
+  / ip dns static add comment=$CommentString name=- type=NXDOMAIN disabled=yes;
+  $LogPrintExit2 warning $0 ("Added disabled static dns record with comment '" . $CommentString . "'.") false;
 }
-:local PlaceBefore ([ / ip dns static find where comment="--- dhcp-to-dns above ---" name=- type=NXDOMAIN disabled ]->0);
+:local PlaceBefore ([ / ip dns static find where comment=$CommentString name=- type=NXDOMAIN disabled ]->0);
 
 :foreach DnsRecord in=[ / ip dns static find where comment ~ $CommentPrefix ] do={
   :local DnsRecordVal [ / ip dns static get $DnsRecord ];