diff --git a/lib/puppet_x/icinga2/utils.rb b/lib/puppet_x/icinga2/utils.rb
index ce578c1f..4d7f5ca7 100644
--- a/lib/puppet_x/icinga2/utils.rb
+++ b/lib/puppet_x/icinga2/utils.rb
@@ -348,7 +348,7 @@ def self.attributes(attrs, globals, consts, indent = 2)
                     elsif value.is_a?(Array)
                       op = value.delete_at(0) if value[0] == '+' || value[0] == '-'
                       "%{ind}%{att} #{op}= [ %{lst}]\n" % { ind: ' ' * indent, att: attr, lst: process_array(value) }
-                    elsif value =~ %r{^([\+,-])\s+}
+                    elsif value && value =~ %r{^([\+,-])\s+}
                       # String: attr = '+ config' -> attr += config
                       "%{ind}%{att} #{Regexp.last_match(1)}= %{expr}\n" % { ind: ' ' * indent, att: attr, expr: parse(value.sub(%r{^[\+,-]\s+}, '')) }
                     else