diff --git a/lib/grape-active_model_serializers/formatter.rb b/lib/grape-active_model_serializers/formatter.rb
index c0d8dae..4711860 100644
--- a/lib/grape-active_model_serializers/formatter.rb
+++ b/lib/grape-active_model_serializers/formatter.rb
@@ -13,7 +13,7 @@ module Grape
           @endpoint = env["api.endpoint"]
           options   = endpoint.namespace_options.merge(endpoint.route_options)
 
-          if resource.is_a?(Array) && !resource.empty?
+          if resource.respond_to?(:to_ary) && !resource.empty?
             # ensure we have an root to fallback on
             endpoint.controller_name = resource.first.class.name.underscore.pluralize
           end