diff --git a/lib/vagrant-libvirt/action/forward_ports.rb b/lib/vagrant-libvirt/action/forward_ports.rb
index 89f641b..8f16a1e 100644
--- a/lib/vagrant-libvirt/action/forward_ports.rb
+++ b/lib/vagrant-libvirt/action/forward_ports.rb
@@ -93,7 +93,7 @@ module VagrantPlugins
             -N
             #{ssh_info[:host]}
           )
-          params += '-g' if gateway_ports
+          params <<= '-g' if gateway_ports
 
           options = (%W(
             User=#{ssh_info[:username]}