diff --git a/lib/server_settings/host_collection.rb b/lib/server_settings/host_collection.rb
index 3c46fae..a2174eb 100644
--- a/lib/server_settings/host_collection.rb
+++ b/lib/server_settings/host_collection.rb
@@ -4,6 +4,8 @@ class HostCollection < Array
     attr_reader :properties
     def initialize(hosts, properties)
       @properties = properties
+      return if hosts.nil?
+
       unless hosts.kind_of?(Array)
         raise InvalidHosts, "hosts: #{hosts} is not array"
       end
diff --git a/spec/lib/servers_config_spec.rb b/spec/lib/servers_config_spec.rb
index 8192c57..580c27e 100644
--- a/spec/lib/servers_config_spec.rb
+++ b/spec/lib/servers_config_spec.rb
@@ -12,6 +12,10 @@
 role2:
   hosts:
     - 3.3.3.3
+
+role3:
+  hosts:
+
 EOF
   }
 
@@ -127,6 +131,7 @@
     it 'can iterate each server' do
       ServerSettings.load_from_yaml(config1)
       expect { |b|  ServerSettings.each_role(&b) }.to  yield_successive_args([String, Array],
+                                                                             [String, Array],
                                                                              [String, Array])
     end
   end