diff --git a/templates/ssh_config.erb b/templates/ssh_config.erb
index e5ab70f..743a15b 100644
--- a/templates/ssh_config.erb
+++ b/templates/ssh_config.erb
@@ -50,13 +50,13 @@ Host *
 # to the original X11 display. As virtually no X11 client supports the untrusted
 # mode correctly we set this to yes.
   ForwardX11Trusted yes
-<% if @ssh_config_forward_agent -%>
+<% if @ssh_config_forward_agent != nil -%>
   ForwardAgent <%= @ssh_config_forward_agent %>
 <% end -%>
-<% if @ssh_config_forward_x11 -%>
+<% if @ssh_config_forward_x11 != nil -%>
   ForwardX11 <%= @ssh_config_forward_x11 %>
 <% end -%>
-<% if @ssh_config_server_alive_interval -%>
+<% if @ssh_config_server_alive_interval != nil -%>
   ServerAliveInterval <%= @ssh_config_server_alive_interval %>
 <% end -%>
 # Send locale-related environment variables