Use null for default host
diff --git a/src/ruby/spec/call_spec.rb b/src/ruby/spec/call_spec.rb
index 4977c10..36a442f 100644
--- a/src/ruby/spec/call_spec.rb
+++ b/src/ruby/spec/call_spec.rb
@@ -137,7 +137,7 @@
   end
 
   def make_test_call
-    @ch.create_call(client_queue, 'dummy_method', 'dummy_host', deadline)
+    @ch.create_call(client_queue, 'dummy_method', nil, deadline)
   end
 
   def deadline