diff --git a/templates/zone-master.erb b/templates/zone-master.erb
index 1722057..5470072 100644
--- a/templates/zone-master.erb
+++ b/templates/zone-master.erb
@@ -17,8 +17,8 @@ zone "<%= @name %>" IN {
   allow-transfer { none; };
 <% end -%>
 <% if @is_dynamic -%>
-  allow-update { <% if ![nil, '', :undef].include?(@allow_update) -%>key <%= Array(@allow_update).join('.; key ') -%>.;<% end
-    -%><% if ![nil, '', :undef].include?(@allow_update_cidr) -%> <%= Array(@allow_update_cidr).join('; ') -%>;<% end -%> };
+  allow-update { <% if !@allow_update.empty? -%>key <%= Array(@allow_update).join('.; key ') -%>.;<% end
+    -%><% if !@allow_update_cidr.empty? -%> <%= Array(@allow_update_cidr).join('; ') -%>;<% end -%> };
 <% end -%>
   allow-query { any; };
   notify yes;