diff --git a/src/ruby/lib/grpc/generic/service.rb b/src/ruby/lib/grpc/generic/service.rb
index 84f1ce75203b30e2bf0d926f4ab2c6fcec98c37c..f5a6b49eb4471d038578c4be81ca769b4538c34d 100644
--- a/src/ruby/lib/grpc/generic/service.rb
+++ b/src/ruby/lib/grpc/generic/service.rb
@@ -110,7 +110,7 @@ module GRPC
         rpc_descs[name] = RpcDesc.new(name, input, output,
                                       marshal_class_method,
                                       unmarshal_class_method)
-        define_method(GenericService.underscore(name.to_s).to_sym) do
+        define_method(GenericService.underscore(name.to_s).to_sym) do |_, _|
           fail GRPC::BadStatus.new_status_exception(
             GRPC::Core::StatusCodes::UNIMPLEMENTED)
         end